muffler packing

Yesterday I took my old drilled out Mac baffle, separated the caps from the tubes, welded them to a new straight baffle, and filled the holes in the caps. I wish the new tube was a smaller diameter ( got it cheap from a local place), but still interested to get some packing and hear how it sounds. This was my first time welding. What's the best packing for this type of setup? I'm interested in quiet operation and low-end power.