I've recently been flying at a location with a density altitude of 8,800' going up to 15,000 plus in actual flight altitude. Undoubtedly he will lose a few hundred rpm but if he props it right it should do fine. Then again, I don't know how heavy the plane has been assembled.

He does not have many options that would fly the plane well that do not also add more weight to the plane. That's the problem. What would work well but not add too much weight to offset the power gain. ZDZ perhaps? 3W-240 is out of the question.