That's way over thinking!! Read the instructions that came with your engine then start flight testing with those sizes until you find the prop that will fly the plane the way YOU, the pilot likes the plane to fly. You don't want to over rev or lug the engine down but there is a lot of testing space between the prop sizes that OS says you can use. Most of my planes I used the LA .46s on flew the way I liked with an 11X6 but the key word there was {I}!!!!!!!!!! There is no such thing as the perfect prop!!!!!