So here is the new template (a bit more aggressive) on your car, if you go out to the end of the trunk it gets you out past the 30% hash, with 0% being the hash on top of the template/roof, 10% is above the c pillar, since you are at the 10% hash to begin with , going out to 35% would net you 37% better Cd, in theory. Your Cd would go from .35 to .22.
Your car is ideally suited for a kamm because flow off the back of the roof goes straight to heck. Its appears as though the designers were thinking when they radiused the area behind the c pillars to draw the air in to compensate for the seriously dropping air behind the rear glass. So this probably does not create a devastating vortex situation, but it certainly is a disorganized build in pressure from the c pillar back.
Any way, I guess my point is, if there was a car that could really benefit from a Kamm, it's yours.
Bigger Version of Pic to Oogle