Ok. guys..I have a "blonde" question..(mind you...I AM blonde!!!

)
I am about to purchase the O.S. Surpass II an .50SX engine. I would love to equip them with aluminum spinners. I found out that the crankshaft is 1/4-28 size, but...do I buy a 2" diameter size spinner or 2 1/4" size??I assume this depends on the propeller size right??
Can you guys educate me here please
Thaaaaannnkkkk you very much !!!