[walke2jd]

I have a 2002 Saturn SL that I have been aeromodding. I'd like to add a boat tail and had an aero question concerning its design.

Would a boat-tail that only tapered vertically and not horizontally still add a large aero improvement? In case that wasnt clear, I would like it to taper from the roof and underbody, but not get skinnier between the tail-lights. Also, the magic number for slope is 10 degrees correct?

Thanks,

Jason