To answer your questions:
1. The mount is on the left tail light of the mini-van.
2. The bottom quarter/third of the hamstick is near the van body.
3. It sticks out to the side and some what of the back.
I chose this method, since the van has sensors on the rear bumper which trigger if any thing is around the back of the vehicle. I had previous experience with having a ham stick mounted on a mag mount and it was fine until the xyl hit 70 mph and it flew off the back of the vehicle.
Kathy, my xyl, has often wondered if position of the van would improve propagation in a specific direction. She thinks that doing the experiment you proposed would be great to do. She is a post masters nurse and computer person, so this seems like a neat idea to her. We are going to be in South Carolina next month and could drive around the island and send test transmissions. We will be in Tennessee in June and could do the same thing. In July we will be in Maryland for work and could also do the same type of experiment. It would be interesting to get several 070 members to participate and see what happens.
Dick - KC3EF