Thanks. The diffuser follows the rear bumper curvature, but mounting it required some trick brackets hidden inside. I cut the bumper in minimal locations as well, didn't need much trimming.
As for the exhaust, I run a single muffler to the driver-side dual tips, and the external wastegate via a long tube to the driver side pipes.
No pics on the build thread since this was an afterthought
I'll have better pics sometime next week.