I believe that I read where that prop is designed to run quietly and be effecient at trainer speeds, say 50 mph, plus absorb that particular engines power at those speeds. I run a three blade MA 12x6 on my .53, the prop hole is a teeny bit snug but I run it that way. Also MA three bladers are balanced at the factory by drilling the hole at the prop cg. I have several and none has needed to be balanced.