The GP42 is a good engine but may be over powering the LT25. Q. Whats the problem with that? A. the LT25 is quite a floater. There is one at our field with a 40 size engine on it and at idle the plane cruises around the sky at just above walking speed without losing altitude! Most of the time the guy has to kill the engine to get it to land. My sons has an 32SX engine on his and its hard to get it down as well. [8D]