Oh yeah, a 1.20 on a plane designed for a .60 will be great. At least until it's time to land and he has to go deadstick just to get it on the ground. It'll make balancing alot of fun too with all that extra weight in the tail.

All a sport plane really needs is enough horsepower to pull vertical reliably. Going up one size to a .75-.80 will do that for you without sacrificing other flying characteristics.