Alpha, I have a flop tite HW zero with a os 1.2 4c turning a 15x8 prop. clocked at 108mph. a model tech p-51d powered by a magnum 1.2 that does 88mph (it has a very thick wing and needs it because it weights a tone). a evergreen p-51d (copy of H9, see thread here on adding flaps for more detail ) pwered by a os 120 pumper turnibg a 15x8 that blows the doors off my Zero (son and I mock combat) , it goes by the zero like it was standing still. my freind has a hanger 9 p-51d with the saito 1.2 turning a 15x8 and flaps it keeps up with my zero,

Your YS adds a 1/2 a horse power aprox. so with a 15x10 you could add 10-15mph to these numbers. Look at the evergreen sold by raiden tech. the wing is very thin.

have fun

Joe