Looking for a home for those small (under 25cc) conversions, check out Chris' new Spad Trainer. http://spadworld.net/viewtopic.php?t=9321 using a 22ccEcho.

His mufflers very nice as well. (after a bunch of searching found where it ID it in earlier RCU post.) First is the manuf data and second is an ordering source. I have spent way to much time trying to fabricate them.
http://www.hammondmfg.com/pdf/1455C801.pdf
http://www.hammondmfg.com/1455.htm
http://www.mouser.com ref the manuf Part#

It's on my project list.