I was looking at your second image,with the 'Template' overlay.
It looks like there's a discrepancy between the height of the Prius,and it's position of a max. roof camber,and the corresponding point on the 'Template.'
This area is extremely important to the boundary layer.
I recommend that you reexamine the overlay.
Anything you put back behind the car is going to help,but if you get it 'right',you'll get the biggest bang for your buck.
And you're looking at a few hundreds of hours of work to create the tail.You sure don't want to do it over.
