FYI
Just for your information I did some nose testing years ago when i was flying airplanes and helies. I took a KB 61 and mounted a length of tubing to the stinger on the muffler. On to that I mounted a 6oz sulivan plastic tank. I drilled 8 1/8" holes in the sulivan tanks and flew the plane. It became much, much quieter. However there was still noise. Then i took two 10" props, extended the prop shaft so that I could fit to props on the hub and bolted both of them on, one in front of the other. The plane still flew well and you could NOT hear the thing in the air. NOT AT ALL.. Most of the noise was the one, 2 bladed prop. Crazy.
The tank muffler did not change the way the plane few at all. And it was much quieter.
Whats the moral of the story? Volume and lots of it in the after muffler.
Mike