I'm about to start fitting the fiberglass tips on the empennage and was wondering what weight of fiberglass mat I should use when closing the ends off? I also found the West Systems supplies locally at a marine supply store.
You'll need some sort of material (wood, foam, even heard of cardboard) to close off the tip... then glass over that. I would say anything in the 2 to 6 oz range should be OK. I used some 2 oz material which I got at a hobby shop. You can always lay more glass on top of that. IMHO, you are just sealing it against the elements.
Using the same 2 oz cloth, I glassed over the seam once I filled it with West Systems epoxy + their filler.
The tan filler you see in the pic is the filler from West Systems. The green colored filler is Evercoat Rage Gold. Dries a lot faster! Only 20 min.