The Pheaton 40 is a great flying plane but does do best with a .60 or bigger engine. Relative incidence between the wings is critical however. A slight change in the upper wing incidence can be the difference between a real dog and a great flyer. If your initial flights are not what you like, try changing the upper wing incidence a bit, this plane seems to like about 1.5 degrees less incidence in the top wing than in the lower wing. Also be sure to put in about 3 degrees right and 3 degrees down thrust; depending on the engine, it might even need more down thrust. Mine was one of two bipes I've had that you could roll upside down and fly hands off with no elevator trim changes.