I found something today that looks like it will work very well.
On youtube I saw a guy talking about modifying a sausage muffler and he was so blase about it,it has to work. So I tried it today and it works very well if you have the right stuff.
You drill out the "dimples" that are holding the muffler together. These are located around the exit hole of the muffler. Mine had three deep dimples. While it looks as though the perforated inner pipe comes out, it does not.
Once you have drilled out the dimples, place the threaded end in a padded vice. I use old cutting board pieces to protect the object.
Take a plastic face hammer and start to rap on the outer edge of the upper half of the muffler body. Keep moving around the muffler. The crimp done by the factory will break loose after a few raps. This loosens the crimp in the middle.
Place a wooded dowel or brass rod into the exit opening of the muffler.
Holding the upper half of the muffler in your hand,strike the dowel or brass rod with a hammer. This will drive the two half's apart.
I did not have real "muffler Packing" and tried fiberglass insulation. It woks very well but will not last as it is blown out of the small holes on the inner tube of thee muffler.
The "muffler packing" is a much better idea if your going to use fiberglass.
I'm thinking that "Chore-Boy" scrubbing pads made of copper or stainless steel will work much better and allow better flow through and still slow the exhaust gasses.
O.k. Back to the two half's of your muffler.
After you fill or wrap the inside of the muffler with what ever you decide to use, shove the two half's back together and twist and align the holes you drilled in the inner tube and the outer half.
I found that there is no room for pop-rivets, or screws. I found Allen set screws works perfectly holding the two half's from trying to blow apart. This way you can replace or try another filler in the future.
I do not have a dB Meter to measure the sound reduction, but it is noticeably quieter. Engine performance did not seem to be effected.
Give it a try,it works very well ,cheap and easy to do.