Do any of you use it?

Being in the construction trade there's a ton of it around.

west system should work for plugs. most of their stuff is intended for marine use. I use raka which is another
brand of marine epoxy. if you want to compare west system epoxy with some other marine epoxy brands, one ocean kayaks has an epoxy comparison test on their web site. it might help you if yellowing is going to be an issue.