I broke in an OS 32SX using a 10x6 2 bladed prop. After about 12 flights it would turn 19K on the ground. I then switched it to a 10x4 3 bladed prop and got the same RPM. IIRC pitch contributes more to thrust than diameter, or the number of blades. In reality, one-bladed props are the most effiecient and provide higher thrust with a high pitch than a 4 bladed prop of the same diamater iwth a low pitch,