If it's getting hot enough to burn wood, you have bigger problems than just finding a sturdy mount for your motor. That's way too hot.

Front-mounting the motor with two screws should be more than adequate. It sounds like you need to reinforce the mounting plate on that airplane. If you use plywood anywhere on an electric airplane, it should be on the motor mounting plate. Too flimsy? Use thicker plywood. Reinforce with tri stock as necessary.