Phil,
Is one of those cars you mentioned the same as the 1964 CD Panhard LM64? I'd read that it has a Cd of 0.13 and could go ~155MPH with the 1L 2-cyl engine.
I'm also curious to learn more about the 1967 Panhard CD Peugeot 66C:
It looks to have a longer tail and the fin stabilizers are slightly straighter.
George, I think you are pretty close in the big picture sense, on the air flow.