RE: Gary Allen 33% Bücker Jungmeister
Kirt, here are a couple of photos of my much modified Bisson side mounted muffler. I didn't want to cut a hole in the cowl for the muffler. I accomplished this by slicing the bottom off and having some custom welding done. The most important thing is to find a skilled welder with an interest in the project. I found one here in Arlington and he does great work. If you go to the Bisson web site and look at the original muffler you can see just how much was done.
After the work on my muffler was initially done I realized that the sound of the straight pipe coming out of the muffler was just too harsh. I cut one of the necked down tips off of the part that I had removed and had him weld it on to the pipe. This made the sound acceptable. As a suggestion, you might be able to take the same muffler and have the exhaust pipe welded on the front side and use some of the curved header pipes to make what you want. A word of caution, the Bisson muffler uses very thin aluminum so reinforcing is necessary. I don't think you want to run a straight pipe without muffling because you probably wouldn't be allowed to fly at most fields.
Here are a few photos of the welding that ASIL Custom Welding did for a friend of mine on a KI-84 scale exhaust system used on a Brison 4.8 twin.