Rick , The best performance in my opinion was with the Saito 150 , superb power and not as thristy as the Saito 180 . The OS 120 flew it very well but I pefered the added power of the 150 . I did build one with a G38 at request of the owner and he quickly decided he wanted it changed after the first few flights (way too much weight). I pulled the G38 off and put an OS 120 back on it for him . I have flown one on a 91fs and was not happy with the power . A cub needs to fly light (like a cub) adding a gas engine adds a lot of extra weight (engine , batteries , etc) and the end result is usualy a plane that looks like a cub but doesnt fly much like one . I hope this helps in your decision of an engine .