[modmonster]

could this be done for a hatchback?

you could imagine a flat clear plastic Plexiglas sheet spoiler coming up from somewhere near the wiper base. it could be supported by the wiper base, sealed at the bottom by duct tape to the car and supported at the top by coat hanger wire run from the hatchback hinges.

this would be much easier to make than a kammback?

maybe you would need a baffle running down the middle to guarantee non-separated bubble formation.

i apologize for crude photo-shop and poor image quality.