Question: I was using a bit of saran wrap the last time out to keep the magnet from scratching the paint. Is there anything else I can use such as a piece of felt?
If the bottom of your antenna is a bit rough and could cause scratches I use a layer of electrical tape, not too thick and is fairly soft. Just make sure there is no dirt or even dust before you sit it on.
Also note that with mag mount antennas that the coax will move due to the wind and over time will mar the paint, so don't just worry about the mount. I know it sounds wierd, but a perminant antenna mount may actually do less damage than a mag mount.