The 028S I have is in great condition, but the muffler had some surface rust. I decided "new muffler!". After I put the new muffler on I looked at the old one and thought "muffler mod!". Here are some before and after pics of the project.
The slots in the baffle were made with a .250 end mill in a Bridgeport (yes an actual Bridgeport... ).
The stack is a piece of 3/4 tube. The outlet area equals +/-85% of the exhaust outlet. The spark screen is still in place.