RE: Tower Trainer 40 what's a good engine?
My neighbor has exactly that combo and I have a Kadet MKll with the 40FP.
10x6 is the prop of choice. I recommend Master Airscrew for a trainer.
The plane and engine combo will do most of your basic aerobatics. It will have limited vertical but will have enough for loops, emmilmans, Cuban 8 ect...