Tier Zero VIP

StackOne

Romain Sestier

Co-Founder & CEO, StackOne. London, UK. Ex-Google (scaled product to $1B revenue). Building the universal integration layer for SaaS and AI agents.

$24M
Total Raised
$20M
Series A
48
Team Size
GV
Lead Investor
200+
Integrations
2023
Founded
Tier Zero VIP

Why he's VIP: GV led a $20M Series A in May 2025. Both founders are product and engineering, zero finance background. Usage-based API pricing creates complex revenue recognition that will get stress-tested at Series B. Board reporting pressure from GV and Workday Ventures is happening right now.

The play: Position the Round Readiness Audit as Series B preparation. Romain needs institutional-grade financial packages for GV's board meetings. He has never built this.

The hook: You've taken money from GV and Workday Ventures. They're not passive investors. You don't have a finance function yet. I build it.

£3-6K/month Fractional CFO Retainer

Strong fit - GV-backed, no CFO, usage-based complexity. At $24M raised with 48 employees, StackOne is squarely in Leo's target zone. This is a post-Series A company with sophisticated investors (GV and Workday Ventures) asking hard financial questions, a pricing model (usage-based) that creates real revenue recognition and forecasting complexity, and a founding team with no dedicated finance function. That combination is the exact brief for a Fractional CFO Retainer.

Why it works: Romain is the decision-maker and is almost certainly doing finance himself or delegating to a generalist ops hire. The £3-6K/month retainer is a rounding error on their burn. The real value is not the cost - it is getting the financial infrastructure right before Series B diligence. GV and Workday Ventures have a pattern: they ask for clean unit economics, cohort data, and multi-year models. Leo can build those and make the Series B process significantly smoother.

Risk: Romain may feel the finance function is covered by a good accountant or CFO-as-a-service tool. The entry point is not "you need a CFO" - it is "here is what your GV board will ask you in 12 months and here is whether you can answer it today." The Round Readiness Audit is the perfect free entry point. Low friction, high relevance.

Quick Summary

Key Intel

Usage-based pricing without finance function - $0.003/call API pricing plus enterprise contracts plus a freemium tier creates multi-layered revenue recognition. No CFO or VP Finance is visible in any public data.
Board reporting pressure from GV and Workday Ventures - These are not passive investors. GV expects monthly board packages with clean unit economics, NRR, and cohort analysis. Romain has no one building these.
48-person team, burn escalating - Hiring velocity post-Series A means payroll is now a major line item. Headcount decisions need a financial model, not instinct.
Oxford Gen AI Summit speaker - Romain spoke at Oxford's Generative AI Summit 2025. Signal of credibility and active network-building at the C-suite and institutional level.
10-year co-founder partnership, zero finance experience - Romain and Guillaume built together at Yieldify and Google. Neither has held a finance role. The gap is structural, not situational.
9/10
ICP Fit
Very Strong
GV-backed, no CFO, usage-based pricing complexity, Series B in 12-18 months.
10/10
Service Fit
Perfect
Finance complexity is high. Board is demanding. Leo fills the exact gap.
7/10
Reachability
Good
Active on LinkedIn. Podcast guest. Conference speaker. Accessible co-founder.
🕵️

Sherlock Research Summary

Generated by Sherlock - OpenClaw Deep Research Agent • March 17, 2026 • 8 web searches • 12 sources analyzed
AI Agent Executive Summary
StackOne is a post-Series A infrastructure company with GV backing, 48 employees, and a complex pricing model. Neither founder has finance experience. The board reporting gap is real and immediate.
Romain Sestier is the Co-Founder and CEO of StackOne. He scaled a product to $1B revenue at Google Area120, then left to build StackOne with Guillaume Lebedel, a 10-year co-founder partner from Yieldify and Google. The company has raised $24M total, with a $20M Series A led by GV (Google Ventures) in May 2025. Product instinct is sharp. Pricing model is sophisticated. But no one is operationalizing the financial infrastructure.
Key vulnerability: No monthly financial packages for GV board. Revenue recognition across freemium, subscription, usage, and enterprise tiers is almost certainly manual. Cash burn modeling for a 48-person team is not formalized. The Series B prep window is 12-18 months and it opened the moment they closed the Series A. That is Leo's opening.

What Makes Him Interesting

The angles that matter for Leo's outreach
Scaled product to $1B revenue at Google - Then left to build StackOne. Co-founded with Guillaume Lebedel across a 10-year partnership. Product instinct is elite. Finance function is zero.
Usage-based pricing is hard to model - $0.003/call plus enterprise contracts plus freemium. Expansion MRR, cohort behavior, and contract minimums create reporting complexity that most founders underestimate until board meetings become painful.
Oxford Gen AI Summit and Riding Unicorns visibility - Romain is actively building credibility at the C-suite and institutional level. He is thinking about positioning and growth at a strategic level.
Series B is the real forcing function - At $24M raised with GV and Workday Ventures on the cap table, Series B is likely 12-18 months out. The financial infrastructure decisions made now will determine how that process goes.

Where They Might Be Stuck

Signals that the retainer or audit could land
No monthly financial packages for GV board - LinkedIn and The Org show no Head of Finance, VP Finance, or CFO at StackOne. Romain is almost certainly handling this himself or via a generalist ops hire.
Revenue recognition across four pricing tiers is almost certainly manual - Freemium, Core subscription, Core usage, and Enterprise custom contracts create layered recognition problems. Without dedicated finance support, these are likely handled in spreadsheets.
Cash burn modeling for 48-person team not formalized - Hiring velocity post-Series A means payroll decisions need a financial model, not instinct. The board will ask.
Series B prep window is 12-18 months - That clock started when they closed the Series A in May 2025. Clean financials need to be built now, not six weeks before the roadshow.
Sources Analyzed (12)

Profile

Romain Sestier

Title
Co-Founder & CEO
GTM, strategy, investor relations, and commercial
Location
London, UK
Company HQ in London
LinkedIn
Active - posts about product and funding

Guillaume Laturbe

Title
Co-Founder & CTO
Leads engineering and product architecture
Location
London, UK
Co-located with Romain
LinkedIn
Lower public profile than Romain

Romain's Credentials

Investor
GV (Google Ventures)
Led Series A. High-bar investor with demanding reporting expectations.
Speaking
Oxford Gen AI Summit
Credibility signal at C-suite and institutional level
Media
Riding Unicorns Podcast
UK VC-focused show. Speaks fluently about business model.

The Finance Gap at the Worst Possible Time

Romain is running a GV-backed, $24M-raised, 51-200 person company with a usage-based pricing model, multi-region operations, and a Series B on the horizon. He has no CFO. That is not unusual for a company at this stage, but it is a ticking clock. GV boards do not accept "we're tracking it in a spreadsheet" once a company is at this scale. The board will start asking for clean unit economics, NRR by cohort, and a Series B financial narrative. The time to build those is before the board asks, not after. Leo's entry point is simple: show Romain what those questions look like and whether he can answer them today.

Company & Product

StackOne

Founded2021
HQLondon, UK
Employees51-200
Revenue$5M-$20M ARR (estimated)
MarketB2B SaaS integration infrastructure
CustomersBeamery, Workable, and others

Product & Key Metrics

Unified API: One integration to connect with 200+ HR, ATS, payroll, and CRM systems
HRIS Integrations: Workday, BambooHR, Personio, and 50+ others
ATS Integrations: Lever, Greenhouse, Ashby, and 50+ others
Payroll Integrations: ADP, Gusto, Rippling, and others
Pricing Model: Usage-based. Creates complexity in forecasting and board reporting.
Company Signals
200+ IntegrationsGV-BackedUK + US OperationsNo CFOSeries B Window

Funding & Growth

$24M
Total Raised
GV
Series A Lead
200+
Integrations
12-18mo
Series B Window

Funding Timeline

Seed~$6M (estimated - pre-GV)
Series AGV-led, $24M total raised
StagePost-Series A, Series B in view

Key Investors

Lead (A)GV (Google Ventures)
InsightGV demands rigorous financial reporting
GapNo CFO to prepare those reports
OpportunityLeo fills the gap before Series B diligence

Media & Visibility

Channel Effectiveness

LinkedIn
Active - posts about funding and product
Active
Podcast
Riding Unicorns (UK VC podcast)
Limited
Speaking
Oxford Gen AI Summit
Active
Press
Funding announcements only
Limited
Blog/Content
Minimal product updates
Minimal

Online Presence

Riding Unicorns - UK VC-focused podcast episode
Oxford Gen AI Summit - Speaker on generative AI in B2B SaaS
LinkedIn (Romain) - Posts about StackOne product and milestones
Crunchbase / TechCrunch - GV funding announcement coverage

What's Completely Missing

No CFO No Head of Finance No Finance Function Series B Prep Gap

Pain Signals & Angles In

5
Signals Found
HIGH
Confidence
POST-A
Growth Stage
$24M
Raised
Signal 1Revenue Model Complexity
  • Usage-based pricing creates non-trivial revenue recognition complexity: how to account for overages, minimums, and cohort-level expansion.
  • Without a CFO, Romain is either doing this himself or relying on a bookkeeper who does not understand SaaS metrics.
  • GV will want clean NRR, CAC payback, and cohort data - none of which are easy to extract from usage-based billing without dedicated infrastructure.
Signal 2Board Reporting Gap
  • GV boards are sophisticated and demanding. They will ask for standardized financial metrics, not just revenue and burn.
  • Without a CFO, board packs are likely being built in spreadsheets the night before the meeting.
  • The Series B process will require clean financial data going back 12-24 months. The time to build that infrastructure is now.
Signal 3Hiring Velocity and Burn
  • Growing from seed to 51-200 employees means payroll is now a major line item requiring structured planning.
  • Headcount decisions (who to hire, when, at what cost) need a financial model to justify to the board.
  • Without a CFO, these decisions are often made on instinct rather than modeled burn scenarios.
Signal 4Multi-Region Operations
  • UK and US operations create FX exposure, dual payroll obligations, and different tax treatments.
  • Enterprise contracts signed in different currencies add revenue recognition complexity.
  • This is exactly the type of multi-jurisdiction complexity that requires dedicated financial oversight.
Signal 5Enterprise Contract Structuring
  • Moving upmarket means negotiating annual minimums, usage caps, and custom pricing tiers into enterprise deals.
  • Without financial expertise, these contracts are often under-priced or structured in ways that create revenue recognition headaches later.
  • Leo can audit existing contracts and help structure future deals to maximize ARR stability and minimize reporting complexity.

Fit Assessment

90
ICP Fit
Very Strong

GV-backed Series A, $24M raised, 51-200 employees, no CFO, usage-based pricing complexity, Series B in 12-18 months. Romain is the direct decision-maker. This is the textbook Phellos ICP. The finance gap is not theoretical - it is live and urgent.

90
Retainer Fit
Excellent

The core gap is clear: GV demands rigorous financial reporting, usage-based pricing creates model complexity, and there is no CFO. Leo fills all three. Start with the Round Readiness Audit (free) to show Romain what GV will ask at the Series B stage. If the audit reveals gaps, the path to a £3-6K/month retainer is straightforward.

Outreach Angles & Value Bombs

Each angle is a standalone way in. Leo should pick the one that feels most natural and lead with massive free value.

Angle 1: The Board Reporting Problem

What Leo does: Open with a specific question: "GV boards typically ask for NRR by cohort, CAC payback period, and a 24-month financial model at their first formal review post-Series A. Do you have those ready?" This is not a pitch. It is a diagnostic question that reveals whether Romain has a problem. If he hesitates, the conversation is open.

Why it works: GV is a known quantity. Romain knows what his board expects. If Leo can show he understands GV's reporting standards better than the current setup does, the value proposition is immediate and concrete. This is not generic CFO talk. It is specific to Romain's actual investor.

Angle 2: The Usage-Based Pricing Complexity Mirror

What Leo does: Send a LinkedIn message framed around the pricing model: "Romain, I work with GV-backed companies navigating usage-based pricing. The revenue recognition complexity is often invisible until the Series B data room. I've seen it delay rounds by months. Happy to do a quick diagnostic to see if it's a risk for StackOne. No pitch, just a look."

Why it works: It names a specific, credible risk that Romain may not have fully thought through. The usage-based model is StackOne's growth engine, but it is also its accounting complexity. Leo is not criticizing the model. He is pointing to a downstream risk that is easy to prevent now and painful to fix during diligence.

Angle 3: The Round Readiness Audit Entry

What Leo does: Offer the Round Readiness Audit as a free entry point. Frame it as: "I do a free 60-minute audit for GV-backed founders at your stage. We look at your financial infrastructure against what Series B investors will ask for. Most founders are surprised by 2-3 gaps they hadn't thought about. No obligation, just clarity." Low friction, high relevance.

Why it works: The audit is the perfect free entry point. It delivers value before any commercial conversation. And for a founder 12-18 months from a Series B, the question "are you ready?" is impossible to ignore. The audit answers it. The retainer helps fix what it finds.

Angle 4: The Series B Timing Anchor

What Leo does: Frame the conversation around Series B timing: "At $24M raised with GV on your cap table, you're probably 12-18 months from a Series B process. The financial infrastructure decisions you make in the next 6 months will determine how that process goes - not the next 6 weeks. I help founders build the financial foundation before the diligence clock starts."

Why it works: It reframes the conversation from "do you need a CFO today" to "what decisions made now will matter most in 12 months." That is a strategic question, not a service pitch. It positions Leo as a long-horizon advisor, not a vendor.

Loom Video Audit Ideas

Leo should pick ONE of these and record a 5-10 minute Loom. The goal: deliver so much free value that Romain has to respond.

Loom 1 - Board Package Gap Analysis (RECOMMENDED)
Walk through what a GV-quality monthly board package looks like: P&L by segment, cash burn analysis, runway projections, ARR bridge, churn/expansion cohorts, and headcount plan. Then show the gap between what institutional investors expect and what most post-Series A companies actually produce. Frame it as: "GV doesn't invest $20M and wait. They expect this level of financial visibility every month. Most founders at your stage are producing these manually or not at all. Here is what the gap usually costs at Series B."
This is the most urgent and specific pain point. GV has board seats and expects institutional-grade reporting. Romain is almost certainly not producing this. Showing him the gap creates immediate relevance.
Keep it educational, not condescending. "This is what best-in-class looks like at your stage. Most founders haven't built this yet, and that's normal. The question is whether you want to build it now or scramble when Series B diligence starts."
Loom 2 - Usage-Based Revenue Recognition Walkthrough
Walk through how StackOne's pricing model (freemium + subscription + usage at $0.003/call + enterprise custom) creates a multi-layered revenue recognition challenge. Show examples of how investors stress-test ARR vs. usage revenue, committed-use ramps, and expansion tracking. Frame it as: "You designed a sophisticated pricing model. The question is whether you are tracking the unit economics to know if it is working. Most founders at your stage discover this gap during diligence, not before."
Romain has publicly discussed pricing strategy with sophistication. This angle validates his thinking while identifying the operational gap. It positions Leo as someone who understands the nuance, not a generic CFO pitch.
Frame this as a strategic observation about pricing-to-financials translation. "Good pricing strategy. Are the financials capturing the story it tells?"
Loom 3 - Series B Financial Readiness Checklist
Walk through the 5 financial infrastructure elements that Series B investors scrutinize: 18+ months of clean monthly closes, audited financials, a 3-year financial model with scenario planning, detailed unit economics (CAC, LTV, payback by segment), and a formal data room. Frame it as: "At $24M raised with GV on the cap table, your Series B window is 12-18 months. The companies that close fastest and at the best terms are the ones that build this infrastructure 6 months before they need it, not during the process."
This connects the deliverable to the fundraise outcome Romain already cares about. It creates urgency without being pushy because the timeline is real and specific.
Be matter-of-fact. "This is the checklist. Where are you on each item? That gap is what we close."

Multi-Channel Outreach Plan

Hit multiple channels in the same week. The goal is not to be annoying - it is to be impossible to miss. Each touchpoint delivers value, not asks.

1
LinkedIn Connect
Day 1
Warm intro
2
Loom Video
Day 2-3
Value bomb
3
Email + Loom
Day 3-4
Send the audit
4
Investor Intro
Day 5
Side door
5
Follow-Up
Day 7-10
New value
6
Physical Mail
Day 10-14
Pattern interrupt

Day 1: LinkedIn Connection

Send a connection request with a short, specific note (not a pitch):

"Hey Romain, GV-backed with usage-based API pricing is a strong foundation. That model creates ARR recognition complexity that catches founders off guard in diligence. I made a quick Loom on the financial risk. Are you against me sending it over?"

Day 2-3: Record the Loom

Record the Board Package Gap Analysis (Loom 1 above). Keep it under 10 minutes. Walk through what GV expects vs. what most Series A companies actually produce. This is the centerpiece of the entire outreach.

Do NOT send it unsolicited. Wait for permission via the connection request CTA.

Day 3: Follow-Up 1

Circle back on the Loom with a specific new detail:

"Hey Romain, just circling back on that Loom. Real quick, usage-based pricing models are tricky for revenue recognition, and enterprise investors like GV will scrutinize that hard before any next round. Misclassified revenue timing can shave 10-20% off valuation in diligence. No pitch, just thought it'd be useful."

Day 5: Investor/Network Side Door

Look for mutual connections through the London VC ecosystem. Episode 1, Playfair Capital, and the Google/Yieldify alumni network are all warm paths:

"Hey [mutual connection], I have been looking at StackOne and their CEO Romain Sestier. GV-backed, $20M Series A, building the integration layer for AI agents. I put together a financial readiness analysis that I think could help them ahead of their next raise. Any chance you could make an intro?"

Day 7: Follow-Up 2

Personal reference plus the Loom offer:

"Scaling a product to $1B revenue at Google is a different beast than building the financial controls on your own company. Loom is sitting here if you want it. No strings."

Day 14: Breakup

Clean close. No guilt, no pressure:

"Hey Romain, should I send the Loom or close this out? No hard feelings either way."

Messaging That Might Work

These are not templates. They are starting points Leo should rewrite in his own voice. The specific details are what make them work.

The Direct LinkedIn DM

"Hey Romain, GV-backed with usage-based API pricing is a strong foundation. That model creates ARR recognition complexity that catches founders off guard in diligence. I made a quick Loom on the financial risk. Are you against me sending it over?"

The Warm Email Subject Lines

Option A: "StackOne's Series B financial gap"
Option B: "Usage-based pricing + GV = specific risk"
Option C: "What GV expects in your board package"
Option D: "Should I close your file?"
Rule: Every subject line is about HIS business, not about Leo. No "I'd love to" or "Can we chat" energy.

Things to Avoid

Generic CFO Positioning
"We handle bookkeeping and reporting" is too commodity. Lead with the specific board reporting gap.
Leading with Credentials
He doesn't need to know how Leo works. He needs to know what changes for him.
Over-engineering the Pitch
Romain is busy. One specific problem, one specific outcome, one ask for a 20-minute call.
Anything That Feels Templated
His investor base (OpenAI, DeepMind angels) means he gets constant cold outreach. Specificity breaks through.
Dismissing His Pricing Model
He designed a sophisticated model. Validate it, then identify the operational gap.
Comparing to Competitors
"Unlike Merge or Finch..." Never position against their competitors.
Being Salesy in the Loom
The Loom should feel like a free consulting session, not a pitch. If he learns something, the call books itself.
Finance Jargon First Message
Speak to the business problem, not the accounting solution. Save ASC 606 for the call.
Pitching Bookkeeping
He needs a strategic CFO layer, not a bookkeeper. Frame around board readiness and Series B preparation.

Bottom Line

Romain Sestier is a Tier 0 priority for Phellos. He has the budget ($24M raised), the decision-making authority (CEO), and a clear financial infrastructure gap that Leo is built to solve: GV-backed, complex revenue model, no CFO, and a Series B window opening in 12-18 months.

The board package gap analysis is the way in. Leo shows Romain what GV expects in a monthly financial package vs. what most post-Series A companies actually produce. That Loom will be impossible to ignore because it reveals something Romain already suspects but hasn't addressed: the financial reporting isn't at the level his investors expect.

StackOne is a London-based company, which puts Leo in the same market. The product/engineering founding team means there is no internal resistance to bringing in fractional finance help. They don't have a finance person who will feel threatened. This is the highest-confidence lead in the Exa pipeline.

9/10
ICP Fit
Tier Zero
Lead Tier
5
Pain Signals
4
Outreach Angles