For what it's worth, I tension the shrouds on my 23 the way Dave has recommended - I do it by feel, so that I can pull the shroud sideways (each of lower and upper) about 1/2 inch by hand. That seems to not overload and the lee shrouds don't droop in a stiff wind. I don't have the same deformation issue, as the 23 has chain plates that penetrate the deck (it has a side deck unlike the 23.5 pictured here) and bolt to smallish wood bulkheads tabbed to the hull.
Off topic some but perhaps interesting: I worked in the Seafarer factory one summer in about 1971, the one on Long Island. The boats I worked on, around 30 to 35 ft, had the shrouds (each) connected to a u-bolt that went through the deck, with a backing plate of some sort (or big washers? I can't recall) under the deck's ceiling liner. No attachment to the hull at all. The deck assembly was in essence glued to the hull using epoxy mixed with chopped glass, crammed into a channel between the flared up deck and hull inside edge. Always seemed flaky to me, and I recall they lost a deck (ripped off the hull) in an Atlantic racing model.
