Saito 82a with a 13X8 APC prop on 20/20 fuel should turn 9700 rpm = 74.5 mph true pitch speed on the ground.
Thats a lot of unloading in the air to hit 113 mph. I have my doubts. I had two Saito 82a, not for my type of flying & too thirsty, it was a good day when I sold them

If you are running the stock or a pitts muffler on your OS 55 you have a lot of un-tapped power left.
A Macs tuned pipe is the best. Or use a Jett or Ultrathrust muffler to keep it simple. 11X7 APC 14000rpm = 92.8 mph true pitch speed on the ground (and unloads well).
I think that 12X7 is too much for the 55. If you think you still need the 12" disc area try a Master Airscrew 12X6 S-2.