beerdead said..
It's 6oz glass covered with PVC. My plan is to fill the void beneath the skin with epoxy and EPS balls from a fruit box, then sand the PVC off and glass a patch over the lot. Any suggestions from those more knowledgeable than myself?

I have done it. The EPS ball trick works wonder, and you only have to "wet" them with very little epoxy to get a result. It then is easily worked with an exacto knife.See: www.gong-galaxy.com/forum/viewtopic.php?p=54729#p54729

I would suggest leaving some room on top of it for a layer of epoxy + microspheres for waterproofness.
Another way is to prepare a very light epoxy + microspheres mix (1 to 7 in volume, 1 to 1 in weight), and add some "glue" additive to get a very light paste that is very easy to work with and apply, and becomes quite hard, so is very easy to sand... I just fixed my toilet plumbing that was in a very tight space this way :-)Others would advice whipping some gorilla glue with water, but I have no experience with it.