John,
3" is a big tube to route out the back but it's still possible. Yes, it's a little more work with the FAB9™ but if you have a talented exhaust guy it shouldn't be too much of an issue. If you need more room, raising the crossmember is an option. That will lower the car but you will be able to compensate with the adjustable lower shock mounts.
Here's a Camaro with the exhaust run out over the top of a 12-bolt. I can't seem to dig up the FAB9™ equipped car.
