[MetroMPG]

Forgive me if you already covered this:

But does flow off the roof re-attach on the trailing edge of the hatchback's horizontal "deck lid" area? Did you ever tuft test that before adding the kammback?

That horizontal section looks too short, which would make re-attachment less likely. If that's the case, Kammy has the potential to make a significant improvement, as the coast down numbers suggest.