OK, this is something I'm working on for my Escort. And one of the limitations that I have is that TOWMBO will
not tolerate any public display of eccentricity.
So, a belly pan is acceptable, but a boat tail is not. Wheel discs are borderline acceptable, rear wheel pants are clearly not. So, I
might get away with vg's, but...
So, my back glass is ~30* from horizontal, and a line from the back of the roof line to deck height at 14* says I need a 8"+ shelf attached.
What does the collective mind know about the +/- of rear window dust deflectors? I know, those are usually only for "wagon" backs, but a deflector with an included arc of 25* would certainly be a place to start. Yes, this would cause lift at high speeds, but at econ speeds, what would be the down side? Would a smooth deflector blade cause more drag than 8 vg's across the back edge?