Installed the exhaust pipe. The biggest challenge was marking where to cut through the cowling to accommodate the exhaust pipe which extends out of the muffler at an unusual angle. To to this, I followed the advice from Homebuilthelp.com - attach a marking instrument to a long piece of scrap and extend the outline of the exhaust pipe port on the muffler down onto the inside of the cowling.
I chose a grease pencil as a maker and a piece of aluminum tubing for the extension and inserted the pencil in the tube and taped it in place. Then I reached down into the engine bay, stuck the aluminum tube up inside the exhaust port, pressed it snugly against one side to align it with the port and rolled the tube around the inside of the port pulling and pushing it to account for the ~30 degree angle down to the cowling.
Once I had the basic oval shape drawn, I drilled pilot holes through the center, each end, and each side of the oval. I then widened the center hole enough to put my Dremel cutting tool through and went to town on the cowling. After several trial fttings followed by an equal number of hole trimming/shaping sessions, the pipe fits through with about 1/4" of space all around it.
All that's left to do is have a welder weld two clips onto the pipe to match the two clips already on the muffler to attach springs in place to hold the exhaust pipe snugly.
Trusty grease pencil inserted into a piece of aluminum tubing to trace the exhaust pipe port.
Muffler on the left, exhaust port near the middle of it and the traced outline on the cowling.
After cutting and triming the hole, the exhaust pipe is installed.