Mr. hill,
I once talked to Ken about engine size and he topld me that they had put some bigger engines in the plane. He can tell you how big. I would think that as long as the engine was within the dimentional limits of the plans and was not too heavy for balance that it should work. As far as power goes, you don't have to push the throttle all the way up. A little reserve power is always nice for those full flap go-arounds.