[Aussie Mike]

Hi David,

I use a 2.5" perforated tube for the baffle wrapped in stainless steel swarf and then fiberglass lagging. the stainless breathes a bit better than the fiberglass allowing the pressure wave into the packing. The stainless also protects the fiberglass from being blown out the tail pipe or shoved down one end of the muffler.

I have to thank Scott for putting me onto the stainless swarf. I've been running it in my bike mufflers and it holds up much better.

A trick I've seen to knock a few dB out of the straignt thru baffle is to crimp the tube a little at a few points along it's length. Just squash it with a pair of vice grips or similar and it only needs to be squashed 1/2" or so. The crimp causes the gasses to deflect and slows them down a bit. It also forces them go into the packing a bit more.

Hope this helps.

Cheers