Then why are we talking about boattails. Working from the front to the back is both cheaper before you get to the boat tail, but easier as well. This is about hood-windshield transition.
This is what was done to aerocivic. As far as the angle goes I am not sure, but I would think an angle meeting up with the top edge of the windshield where the roof begins would help and it somewhat bisects the difference of the hood-windshield transition.
Aerocivic - aerodynamic mods for maximum fuel economy - aerocivic.com boat tail storage space
J