I don't know that much about the electric motors but I think i could be the prop you are using causing the motor to spin to fast. All I know for sure it the recommended prop for that setup is a 11 x 4.7. That is what I am flying. Mine hovers at just over half throttle but that makes finding the sweet spot easy and it still jumps out of a hover great. Maybe you should try one and let us know if that helps the heat issue.