More progress! Almost wrapping it up! I had a clone of the Vorsteiner spoiler from RW Carbon, and the thing apparently won't lay flush at all on the car. The shop i'm working with is even a dealer for them, and just says it's a totally bad part. Unfortunately, that makes 2 spoilers i've gone through with RW trying to get a decent piece. The first one had clearcoat issues left and right, second won't fit at all.
So now i'm just ordering a legit Vorsteiner part to close this out. Here's some updated pics!