Originally Posted by kingcan
But as DrB suggests, we're feeling a little leery of the wood/water/seacock combo and planning the fix without wood (considering brass).
I would not advise brass. Solid fiberglass is much better as it will expand and contract at nearly the same rate as the hull, will be a permanent fix that will never need replacing, and won't suffer from galvanic corrosion issues.
If you don't want to make your own backing blocks McMaster Carr sells Garolite G-10 in 1/2" and 5/8" thicknesses which is a fiberglass/epoxy pre made panels. It's pricey but amazing stuff.