Mounting the mast through the passenger side car window is another simple method. Just secure the mast near the top of the door frame, and drop the bottom through the door handle or whetever is available. This will create a lot of wind noise and may make the car somewhat uncomfortably cold for the beam turner, but requires no permanent changes to the car.
A popular solution for avaid hunters is to build a frame for
a sun roof, or punch a hole through the roof. While it may
take a couple hundred dollars off the re-sale value of a car,
it provides a very comfortable, quiet, and secure mount.