C-pillar, not B. Looking at the lift back, I noticed the same problem you did. I’ll work around that and try as best as possible to keep the transition smooth.
You don’t think a small gap, I.E. 1/4”-3/8” would cause the same problem? I imagine it would, but maybe not? NACA ducts will be probably have to be made from fibreglass and riveted onto the glass.
(Photo from Australia)
Here’s a little sketch. Vaguely reminds me of an RX7. There was a 75MPG Civic VX build on here that I really liked, and I think I’ll copy it’s rear wheel spats. I’m considering cutting out sections of the rear bumper, to make it look sort of like the Porsche Can-Am 917/30 and similar cars. Might end up collecting dirt due to the turbulence in the wake, but maybe it’ll be okay.
I should do some larger images, and use a scanner/laptop instead of this stupid phone.