A note about deck coring: The standard drill, epoxy and drill method has some major flaws. The epoxy plug is brittle, and may not be able to take compression loads without cracking. IMHO it only seems
to be effective since the bedding compound is actually keeping the water out.
I think a far better solution would be to bond fiberglass or brass tube between the upper and lower skins for high load applications. When I rebuilt my bowsprit, it originally had 4 1/4" bolts through the deck with the epoxy plug method.. The holes were badly distorted and water had penetrated to the core. My solution was to drill from the bottom just into the upper skin, I then saturated with penetrating epoxy. After the epoxy dried I coated 1/4" NPT pipe nipples with thickened epoxy and threaded them from underside up to making contact with the deck skin. I then ground them flush. My bet is this system can handle far heavier compression and torsional loads.
Anyone else try anything similar?