Core flow for the conversation 1) Open collaborative

Start aligned, not defensive:

“I’ve been thinking more carefully about the interest rate topic.”

2) State the issue plainly

Keep it simple and firm:

“I’m not in a position to deliver what the synopsis is describing within the timeframe.”

3) Briefly anchor why (constraints)

Don’t list everything—just enough:

“The direction needs reworking, and I’d need to build more technical depth. I don’t realistically have the time to do that properly.”

4) Name the risk (this is important)

This is your strongest point—keep it:

“It’s quite an ambitious topic—it sounds good in a synopsis, but it’s hard to execute convincingly. I don’t want to present something that isn’t properly backed up.”

That lands well in an actuarial context.

5) Offer options (stay constructive)

“I do want to contribute though. I think there’s a good piece in the broader area—maybe around where PCA struggles and how you might bring in structure or priors—but as a lighter, more conceptual piece rather than a full technical build.”

Then be explicit:

“I’m not comfortable leading a full technical section on this as it stands, but I’m happy to support with something more contained.”

6) If he pushes / gives timelines

Hold your line calmly:

“I’d rather commit to something I know I can deliver well.”

7) Close (keep it open, not uncertain)

Your current “I’m unsure” sounds a bit weak. Better to sound measured:

“Let me think about what shape of contribution would work best from my side and come back to you.”

Subtle but important tweaks Replace “I’m unsure” → with “let me come back with something concrete” Replace long explanations → with clear positioning + options

Keep repeating (if needed):

“I want to contribute, but in a way that’s deliverable.”

One thing to watch

If he says:

“It can just be high level”

That’s where you respond:

“Yes, I’m happy with high level—but I still want it to be something complete and well thought through, rather than something still in progress.”

Bottom line

You’re not saying:

“I can’t do this”

You’re saying:

“I won’t overcommit—but I will contribute properly”

That’s a strong, professional stance.