Wow very nice! Can't wait to see the results on the run.
When you get this tested to really see what you have, I have another addition I've always thought of and thought I would throw a mock up out there.
Its horribly ugly and just a suggestion, but I have always wonder about air deflectors and recombinors (not a word) around the lower section of the exposed wheel. I would think ABA or tuft testing would show some benefit, I'm not sure how bad the air is off the wheel, but this would be a triangle or rounded shape to try to match the air off the wheel and smooth it into the tail.
I figure it should be about the same purpose as the humps on the back of old open roadster race cars, like this porsche has:
Anyway just a thought for future discussion.