I still fly a OS .46 SF in a Sig Something Extra and use a APC 11 X 4 which seems to be the largest prop the engine will run reliably with. Although I am sure this older .46 produces less power than the new .46's. Still gives the plane decent speed and a nearly unlimited rate of climb. One thing nobody else has mentioned here is if your plane is light with a low wing loading a higher pitch prop could cause your plane not to want to land, in which cause regardless of performance you will want a smaller prop.