Back when I had my Pioneer AVIC-N4 installed, I mounted the sat. antenna next to the the VX radio antenna and ran the wire through the base. I noticed during that time that my base was pretty dry-rotted. I removed it and coated it (thinly) with black RTV and after drying re-installed it. I haven't looked lately but I'm pretty sure it has held up over time.

NOW I'm going to HAVE to LOOK....thanks alot guys...lol.