[MetroMPG]

I have a feeling the angle of your rear hatch glass may be in the "BAD" zone.

If I hadn't lent my Hucho book to Ben, I could verify the numbers!

But the idea is that as the rear angle descends from horizontal, drag decreases to a certain point, then increases dramatically at a certain angle (where strong C-pillar vortex formation begins to occur), and continues dropping again as the rear glass angle approaches vertical.