Ugly ugly ugly system that works amazing:
The metal simply wedges into the seam of the rear hatch.
I could almost stand on the very end of the tail and not worry about it and not worry about it. I'm going to have to do something about the hitch mount too. but for right now I want to get it road worthy and then I'll worry about cleaning the air on the bottom. (Less worried about it there since the back of my car isn't exactly smooth with the lack of underbelly panelling and hitch hanging off the frame already)
BUT! I do have a fairly smooth front and middle:
Screw those belly pans that are gonna get dented. Give me 1/4 inch thick 6061 aluminum.