[Christ]

The bike has 1.5" primaries. With this pipe size, I think I have enough room to literally tuck the pipes under the bike with a collector, and still have the collector and muffler under there, never actually leaving the space under the frame. This will free up alot of space down the side of the bike's frame, leaving more room for bags and possibly helping the aerodynamic profile?

That would give me about 3.5 feet of total exhaust length, and the muffler should still keep the bike fairly quiet due to it's proximity to the ground.

Even straight pipes are quiet when they're aimed at the ground.

Anyone have any suggestions further than that?

I'm thinking basically to keep the 1.5" pipe diameter, running into a 2.25" collector so I can use Larry Widmer's straight through muffler design. The pipe will be angled slightly out from the frame so that it doesn't exhaust directly on the tire while stopped idling or at low speed, where it could cause some damage to the rubber of the rear tire.

So I'll end up with a single muffler, blowing out the right side, 1.5" primaries about 30 inches into a 2" pipe (the 2.25" collector is to make up for the space of the muffler packing) which will make up the remainder of the exhaust pipe, vented slightly to the right.