I’d be remiss if I didn’t give a shout out to Bob Fine who showed me how to set up new seats for deck hardware that should easily remain water tight for more than 30 years. Shown is an inside view looking upward to four epoxy filled 3/4 cylinders in the deck that are ready to be drilled for fasteners. The original fastener hole on the deck side is preserved by using the hole saw cutting from the inside fiberglass through the balsa core up to, but not through the deck skin. After cleaning the hole, Gorilla tape is used to cover and epoxy is injected from the deck top.
Thanks much Bob!