I agree with Ace Bogie on the engine choice. For the price/power ratio, ease of use, depenability and sturdieness, the 25fx is the best choice. It's only drawback is the rear needle valve tends to break off in hard crashes. If you score the mounting arm about 3/4 of the way through it will break off in a way that doesn't damage the back plate and let's you re-mount it with a wire tie in a jiffy.