tcrcc

Guys:
I am building a 46-sized Extra 300S (Phoenix) and have two questions about the cowl and muffler. I have fitted the cowl around the engine head / glow plug but find that (in distinction to the photos on the box) it looks as if I will need to relieve the cowl around the muffler also. Is that correct, or do most of you use Pitts mufflers with a cowl?

Secondly, with the engine mounts located properly, and the engine spaced from the firewall according to the manual, I find that the stock muffler does not quite clear the bottom of the airframe. Do I need an extension between the exhaust port and the muffler, or should I cut away at the bottom of the airframe?

Thanks
Bill