Roy, your analogy of the car body as a tin can really got me to
thinking.

With the whip mounted dead center on the top of the car, I can see how
the roof acts like a ground plane (a very short one) but I'm puzzled
about the radiation from the lower part of the car body. If one
visualizes RF flowing through the sides, hood and trunk of the car, the
currents will all be in phase with each other (roughly, of course) but
the currents are displaced in space by several feet.

How does this affect the net radiation from the car body as a whole? Is
there some addition or subtraction due to having the same current, same
phase but at a different location in space, and arranged in a more or
less 360 degree pattern?

An interesting thought.

73, Bill W6WRT