Sorry, but no dice. He has a plane, and unless he's willing to modify it, the total engine/muffler/nose weight that is needed to achieve the correct CG is fixed. As long as his engine/muffler combo does not exceed the weight needed to achieve the correct CG, the wing loading is fixed regardless of the engine chosen. Your welcome to worry about the wing loading but its a meaningless exercise (again, unless your willing to modify the existing airframe).