Mike,
This may not be what you are looking for ... I went with what ERA calls out for their under car exhaust, but had it turn out before the rear tire. Not as efficient as a straight through setup, but it works well and looks pretty good to my eye. Not too loud but not to quiet either, just the right amount for me. An exhaust system is pretty much a balance between power, clearance and sound.
At the bottom of page 22 and top of page 23 of my build log is the setup:
ERA 2136 Build Log