The 11x7 is a break in prop, and suits the engine just fine: turning up to 14000 rpm... while still rich. It is a ringed engine after all.
I have a .61 HP Gold Head that will spin an 11-7 prop at 13,800 on a good day. IMO that engine will need prop with more pitch to make your plane go fast! Maybe an 11-10 or 11-11.