I'm worried about water getting under the mag and rusting the spot it's sitting.Mag mount is your only option if you don't want to mar the paint. Every other option requires clamping a mount to the edge of a body panel (the clamp screws have to pierce the paint to get a connection for proper grounding), or drilling holes.
A mag mount does minimal damage to paint if both the mount and the paint are clean. Any dirt will get crushed into the paint and mar the surface.
Are these ok mounts? http://www.theantennafarm.com/catalog/tram-1246b-1571.htmlI would suggest a fender bracket mount:
Properly installed NMO mounts do not need any kind of sealant..You can put sealant on the mag mount base to prevent water intrusion. If that is not an acceptable option, then your only option is to drill hole(s). And you'll still need to apply sealant around the mount.
No. They work, but they will damage the paint.Are these ok mounts? http://www.theantennafarm.com/catalog/tram-1246b-1571.html