I checked my Brisen and found out it is a 2.4 (39 cc) so it is a perfect match for the plane. I mounted the engine last night and the cowl clears the engine with room to spare (inverted) but the plug will need to show a bit. The pits muffler is going to require some cutting of the firwall at the bottom to provide clearance, as the muffler will stick past the fire wall 1.2". When done it will be all hidden by the cowl with only the exhaust tubes projecting as designed. To in fill the cut out area, I think I will either take some thin wall alum tubing 2 1/4" outside diameter or so, and fit this back into the cut. The other choice will be to laminate up some fiberglass around a tube and make a custom filler. In either case, I will wrap a dowl with course sand paper and clean up the cut to create a nice concave that will match the muffler bodies shape. I doubt the cut will weaken the fire wall as only a small portion of the bottom needs to be removed (about the bottom 2", from left to right). Once I have it cut I will be able to determin if it needs any addtional reinforcing.

I also found the light springs I was looking for so I can modify the tail wheel doors to avoid the elastic bands.