There is a lesson here about props. That 10-9 prop is the wrong choice for a mild 40 engine, flight training, or accelerating out of a jam. High pitch props do one thing, basically, and that is generate straight line speed. A high pitch prop will lessen the plane's rate of climb and lengthen the takeoff roll. Lower pitch props generate less speed, but climb and accelerate better. And that's what you want in training and sport flying. Modern 40s do very well on 11-4 and 11-5 props. APCs are generally more efficient than Master Airscrew, for instance. Experiment until it flies the way you like.

You didn't say which Kadet you have. There is quite a bit of difference between the Mark II, the LT-40 and the Seniorita/Senior designs. But the power you've got with either of those engines, should fly the socks off any of those planes if the engine is running well and it's propped right.

I believe, too, that the idea that you just strap on a &*^& load of horsepower to whatever you fly and depend on it to keep you out of trouble is short sighted. What happens when you get yourself into some odd flight attitude and that SuperGrunt 77 craps out and dies? Now you have to know how to use the wing and the controls to get it down in one piece. Learn to fly the airplane, not just the engine. I've been futzing with RC aircraft since 1970, and I still do dead stick practice nearly everytime I go out. The game is to climb nearly out of sight, kill the engine, trim the plane for a glide, and land it so that you can turn it and stop at your feet. Then you really do know how to fly and not just point the thing and open the throttle. I'm still trying to make a landing that nice.....