use my tech section index below and look up the hartman mod

also dragbikemike has many improvements to show you.

In the world of mufflers, fiberglass is not "baffling".  Baffles reduce noise by forcing the hot gasses to change direction.  The directional changes scrubb off acoustic energy.

Fiberglass and ceramic wool are used to absorb energy.  Those products are used to surround a perforated tube.  The hot gasses flow through the center of the tube, not through the wool packing.

You are correct about the stock muffler.  There is no wool packing used in the stock muffler.  The stock muffler relies on directional changes and restrictive tubes to reduce noise.  It's real good at scrubbing off noise, but real bad a allowing the hot gas to flow freely.

It's a complicated contraption.  You can improve flow dramatically and still maintain a quiet exhaust system, but it requires a good understanding of the flow path and the various components and chambers within the muffler.  I think this post will give you a very good idea of what you are wrestling with.  You can make some decent power with the stock muffler, and you don't have to make a lot of noise in the bargain.

http://suzukisavage.com/cgi-bin/YaBB.pl?num=1526453881

Hope this is helpful.  Let us know what you come up with and how it works.

The stock muffler sometimes sounds like an old VW. If you've ever heard a VW whistle, you know what I mean.