Doesn't matter what you pack it with, it degrades and blows out in little dust particles. Kind of cool at night, quite the spark show. Well, unless you can get your hands on some Navy surplus or USFS surplus woven asbestos firefighting blanket. I DO have some of those squirreled away somewhere from my wildfire supression days.
At least you don't have a Vance and Hines, Hard Chrome, or Roadhouse pipe...the baffles have a tendency to shoot out at a high rate of speed. Usually with Kojak behind you.
Swing by a shop that carries V-Twin Mfg parts, you can order decent baffles, cheaper than you can make them.
-WD