[aerohead]

Since so many of the members have notchback cars I dug deeper into Hucho's book and SAE papers.Here are some of the things we have to consider which affect the back of the car:
*roof curvature (camber)
*roof transition to backlight header
*angle of backlight
*transverse curvature of backlight
*C-Pillar contour
*trunklid (boot) height
*trunklid (boot) length
*percentage of this area compared to the overall length of the car
*quarter panel boat-tailing
*underbody of the car
*presence of a diffuser or not
*presence of wheel skirts
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This sort of 'knowledge' has been around since 1976,so there's a good chance that Toyota has already 'optimized' the Camry in the Japanese Auto Research Institute (JARI) wind tunnel.Toyota may have their own tunnel.
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A comparison to the 'Template' might tell something.Many 2013/14 cars have the 'Template' running right through the center of their spoilers.This wouldn't be arbitrary.