Danshutz, I have had great results using conduit as exhaust. I have used it right against the flange and never had any heat issues or failures. I use the galvanized electrical stuff that's easy to bend and weld, although it is nasty stuff to weld. Be sure to only weld it in a well ventilated area. The smoke from it can cause SERIOUS health issues.
It's easier to bend conduit to fit than it is to piece bends together from handlebar chunks. Less welding too!
Here's a pic of the latest low pipe for The Pig.
(No conduit in this one since I only needed one bend)
If more is better, then too much is just enough.
If you can't afford it, build it yourself.