A 2 Stoke .91 is going to give you gobs of power, but cowl clearance and prop clearance may indeed be an issue.

When a model is unknown to me and I'm going 2 stroke, I always go with the biggest recommended engine.

That way I know it will fit.

You are NORMALLY OK going larger, but there are always exceptions...

Frankly in the 2 stroke world, I've never been unhappy with the largest recommended size.



I can't say the same for 4 strokers though, as I always wish for a bit more power than the largest recommended or I end up with an oversized engine.

e.g. a 1.40+ in a plane that calls for a 1.20 FS etc.