RE: Jett Stream for OS 55AX
Listen to Bob, the max APC prop you can run with the Jett muffler is 11X6 for best performance. You can run a Master Airscrew S-2 Series 11X7(dark gray) , I actually prefer this over the APC in this application for ballistic vertical power and speed.
The muffler pressure is fine with the Jett muffler. If you have pressure problems with this, you would with stock muffler or tuned pipe as well. The H9 Phoenix 7 shows the engine mounted sideways, this is carb optimal for acrobatics.