I thought I would post this, but I would not be surprised to find that others had already worked the fix.
After a couple of years, my muffler mounting holes had become pretty sloppy. Since I had a little time on my hands, I fired up the handy wire feed with aluminum wire installed, and welded both holes closed. One cooled, I used my verticle belt sander to flatten one side for drilling. I started with a small bit, and worked my way to a 5/8 bit. From there, I used a carbide cutter in my dremel to open the hole up just a little more (the hole is smaller than a 3/4, but bigger than the 5/8. Since I didn't have a bit in the middle, the dremel removed the little extra material needed to install the new rubber mounts.)
At the same time, I tossed the whimpy little rear mounting bracket (I've broken a few of these), and made a new one from 3/8 aluminum, polished to a mirror finish. Since the new bracket does not cradle the rear rubber mount, I used a washer on the inside to keep everything secure.
Now my muffler will last at least another year.
Rick