dump port pipes?
if your going to "fabricate" a silencer it dosent matter what you start with. the dual in dual out single silncer on my yfz450 took about a day or so to build from 2 seperate silencers. no i havent got the bike done and no i dont know what its going to sound like, and yes it has a banshee motor in it, i just built it cause i felt it was a cool way to do a silencer.