I have to disagree that you can't have too much power. For your IMAC application a Taurus 52 would be overkill on a 27% bird. The reason relates to the size of the prop. Larger engines require larger props. Larger props can cause ground strikes more easily and generate more torque that has to be dealt with while flying all the time. You can use a three blade, but they not as efficient. I always argue tthat you should "let the engine match the application". If you want to do 3D, fine, but if you don't, then a smaller engine can still give you unlimited vertical (desirable) but not provide the overkill (or price) you don't need.

I am flying a bird of my own design that has an 82" span and weighs 16 lbs. It has a DA50 and that is insanely too much. It accelerates up on 1/2 throttle! If I did it again I would probably put on a 35 to 40 - a G38 converted, for example. I have a G38 on a 15 lb giant Stik and it also accelerates up, but at full throttle.