Hey junkless, a friend of mine dipped hers in something, liquid rubber, I think. When I get back to town next week I'll ask her about it.
I use marine silicon and make a perfect bead all the around my coil cover on the Excal. It's sealed. No sand, no chips from banging into coral balls, shells. It will stay sealed (if done properly) for a good 6 months or more. I learned NOT to wipe the bead of silicone, as when you do have to change it, it's a pain. Just keep a big bead all around and it will remove easily, when time to reseal.
Just my 0.02 worth.