A 65 is definitely too big, but it was left over from my sons last aircraft and so we avoided buying a new engine. We just limit the travel on the servo to limit the power.

By the way, this aircraft is superb. My son has been flying for a few years, and he's my instructor. With his help I was able to solo the Kadet (this morning) after just three weekends of practice (about 15 flights total). This thing flies like a big powered glider. It is very slow in the pattern, and that gives a student time to think about what is happening. It's probably a bigger step up to a second aircraft that flies faster than if you started with one of the smaller 40 size trainers, but that's OK. I suspect that soloing more quickly would keep more new folks in the sport. In any event, if your're new to RC and want to fly on your own quickly, the Sig Kadet is a great way to start.