Thanks! I really appreciate the feedback.

The price of the options eating into returns is reflected in the number we present (we assume a consistent valuation growth by stage and at exit), but taxes aren't and those can 40%+ in the US, which people don't necessarily expect. Limited exercise windows are one of the things we have in the list of ways this can go horribly wrong, but you are right that it is something that you can plan for if you know it's coming.

Thinking about it, that and early exercise might both be candidates for some sort of "list of questions to ask" tool...