Please help me with ideas for a rear hatch

[myrefugeisintheLord]

I would agree. My CRX has a steeper hatch angle, yet there has been tuft testing to prove that the air is attached to the hatch. (Which was a selling point to me.)
Example:


I'd go with that last concept you had Razor. You might even look into whether it would be good to taper up that last angle a bit, like the CRX too. ???

Oh, will you be keeping the spare tire on? Your last concept might not allow for one.

[PaleMelanesian]

Consider tapering the sides in as well. You can probably get more wake reduction that way than you can vertically, since there are two sides.

[RedDevil]

The windshield is pretty much upright and the roof is flat. Maybe put a curved plate or bulge on top to make the transition more fluent. Further back it can already bend down a bit so the rear section can bend down further without detaching the airflow.
In the whole it should look a bit like the Insight's and Prius' roof line, only considerably higher.

[razor02097]

no spare tire I have a pump, tire plugs and patches and a bottle of slime. I took the jack, tire and brackets out which saved almost 72lbs. The rear seat belt towers are gone as well as the rear seat. I essentially have a 2 seater with a good size cargo area. Good ideas about tapering in the sides also.