[Christ]

So what I'm thinking about this all - That's a nice Kamm first of all... a slightly steeper angle might work out a little better for you though, as was noted earlier. Would it also not work out better for you to move the sides out to the absolute side of the car, then taper in 13-15* from there?

there was mention of why the Prius had a turn-out for a deck lid on the back... the overall angle from the upper edge of the deck lid to the highest point on the top of the car is enough to keep attached flow even though there is obviously some airspace there. This is to say that even though the overall rear descent is more than 15* (is it?) the outspat (is that a word?) of the rear deck is enough to "adjust" the angle of flow descent without negatively impacting aero. Lay a piece of wood (or something) from the roof line to the tip of the spoiler-ish deck lid, and figure out how much airspace is in there... might give someone an idea...

And please, someone correct me if I'm wrong about that.