What is the criteria for determining the size to use when going to a three bladed propeller. Specifically, I am putting together a Hanger 9 P-40 and powering it with a Magnum .80. Although a three bladed prop is what the real P-40 used, this is not necessary for my model. It may be that 4 strokes shouldn't use 3 bladed props, I don't know. Need some GOOD advise.