One of the guys at our field had a tower trainer with an OS LA 46 on the nose. He originally had a MAS 11x5 prop on it. Took most of the (grass) runway to get the plane in the air. He switched it to an APC 11x5, and now the same plane gets off the runway in about half the distance. The APC, for the same pitch prop, seems to be much more efficient at translating the engines power into pull. Not a faster prop, just more efficient.

Brad