nexxa

Thanks for the answer. Ok square at tip.

I will tach my original APC 10X9 firts and reduce the diameter by 1/4" at the time. I want something like 14 000 - 14 500 on ground. If finally the diameter is 9", I will order some.

I use Ultrathrust racing muffler on my OS.55AX. The engine at the moment don't rev enough, It takes a lot of time to the engine to go on tune and gets extra rpm... I will help him a bit!