About an easy-ish way to calculate a firmer frontal area for the Z:
Mark off a known distance (3 ft or whatever) on a straight surface on the front of the car. Back the car up to a white wall or anything that will stand out easily and take a head on picture. Drop the image into CAD and scale it until your marked measurement jives with the drawing scale. Draw a shape around the outline of the car and have the program calculate the area. The position of the camera (say at bumper level) might throw you off a bit because the camera would be looking at the roofline at an angle from that position and wouldn't be a true head on profile.
