Hi there I was wondering if a gms 76 would be too big for a chipmunk 61 inch model, it says to use a 46 two stroke or a 70 four stroke the weight of a gms 76 is 700 grams and an os 70 four stroke is 500 grams. There is no point using a gms 61 they are the same weight as a 76

There's only one way to find out. Try it. I stuck a .61 in a Pilatus designed for a .40 and am pleased with it. The main thing is that the aircraft will be heavier as you will want to beef it up structurally. It will also increase the wing loading and might be even more prone to tip stall. The good part is that you will have plenty of power.

A 76 on a 40 size plane may be ok, if you are a VERY good flier, and like flying rockets.