I recall the pictures from somebody, who used a holesaw and made round recessed fittings with a tube-shaped peice of wood and a SS peg thru it, with a bottom under the whole affair.

I'm intending to do that with my Walrus, and thought I'd practice on the Tred Avon since it has no deck lines. Problem is, the Tred Avon has no hatches - access into the ends is thru a 4" porthole in the bulkheads, mostly just so I can air it out in there. Is there a way to install the recessed fittings without access underneath the deck?

Suppose I cut the holes, made the tube-shaped pcs. Then notch them for top installation of the cross-bar. Then install them into the deck, reaching underneath with schmutz to paste them in place. Then install the bottom, then slide the cross-bars into the slots and fill from above with schmutz. Only the notches would actually show, if I could get the bottoms to stay in place long enough for goodge to set.