The location where the antenna mast mounts to the van is at the top-inside of the van door well. Its not on the door. This location is under the drip-edge of the roof so water is not likely to get to the screw holes. However, I put a good amount of caulk behind & in front of the mount to prevent rusting.

I'll get some pics up and see about adjusting the resolution.

Tron Of Borg