I still am not completely satisfied that we have adequately addressed how to duplicate the Streamlining Template, especially for those of us who need to render this shape for tails on our cars.
To help determine how to duplicate this shape, I downloaded the "C" version, straightened the "road surface" in a photo editor, then placed that copy in a 2D CAD program, and started working.
The first picture shows the "C" template with some geometry applied. You can see that a radius of 5.64 times the height of the car body provides a very good curve fit of the aft curvature down to 21° slope.
This is a closeup of the curve fit to AeroHead's rendering. Very close indeed.
I would have to say, overall this method gives a very close fit to AeroHead's standard.
Jim.