A prior owner had drilled out the muffler to try and improve the sound, instead it sounded like a bike with holes in the muffler. The pipe on the GS500 doesn’t take a slip-on well as it has a bend right at where the muffler mounts, and used stock exhausts started around $100 for a system with rust & dents. So fixing what I had seemed to make the most sense.
I welded a cap on the end of the muffler, drilled it out for the center pipe and welded that up too. Then it got a quick coat of high-temp paint. Looks a bit lumpy up close but not too bad, and fixed the muffler sound.