Here are some various car rigs that I have done. One is for mounting a flowcine with Ronin to the back of a truck. The 2nd one is a hood mount with overhead diffusion. The 3rd rig is a hostess tray but the height can be customized. The other pictures are various DSLR mounting options.
The Mirror Rig - This rig was built to hold a mirror that was reflecting light through a window. The mirror was being sprayed with water.
The Camera Flip Rig - This rig was built so the camera could go from under slung to upright with one move. The grips were able to rotate the camera using the handles on the end.
The Ladder Rig - This rig was built to be able to mount the camera higher than a tripod. It has 4 points of contact and is very sturdy.