The exhaust system was not to my liking so I purchased a wrap around Pitts Style to replace it with. It's kinda big and still wouldn't fit under the cowling but I made it work so about half of it is sticking out and is really not a big deal because it is the same color as the covering. I had to cut out around the muffler and engine head and make a slot for the spark plug wire.
I used the cut out parts to re-enforce the areas of possible stress. You can see where I glued it in. Sorry the one picture is not clear.
I also did not like where the exhaust stacks where so I made a little cut in them, bent them over slightly to be in the middle, and welded in place. It's nice to have a welding shop sometimes. I do a lot of welding on muffler for RC Flyers. Especially on Evolution 3pc mufflers. You can not keep them from spinning around so I just weld them all around. This stops the spinning around and even helps keep them tight against the engine port.
You can see in the last picture the edge of the cowling and the muffler and how much it sticks out. I thought about modifying the thickness too but will wait until I peal, glass and paint it. That will be after all the bugs are worked out and I get to fly it 50 times. You can also see where I put the LIFE 3200 and 2200mah batteries and the ignition module. I wrapped the batteries in some RF prof material and foam. I had to route the spark plug wire around the muffler.