Gentleman, thanks for the feedback. The prop is the recommend size for engine break in. The reason a muffler was not used is the pitts muffler I have for the engine will not fit without major firewall surgery. I found an old Super Tiger 3000 pitts muffler that fit. It has been installed and tomorrow, weathering permitting, I will try it out. Where I fly a muffler is not required. The nearest house is several miles away. Once again, thanks for the info.