Those "pegs" are there for the prop to rest against. They will supposedly allow the spinner to then fit over the prop 'prop'erly. It seems 75% of the time, they still don't fit right for me, but....

What a65l was referring to was the "spinner" (at the notches) touching the prop baldes, not the backplate). You should sand or carve a bit of the spinner 'slots' if they touch the prop.
Dennis-