Now that I have a boat, I need to replace a couple of
gate valves used as seacocks.

Nigel Calder et all recommend using a wood block and bronze
bolts to secure the seacock to the hull, rather then simply
screwing it to the through hull. Makes sense to me.

The diagrams all show a perfectly flat hull, but as we all know,
real hulls are generally curved. My question is: what's the
best way to contour the wood block (actually a ring) to conform
to the hull? Any hints?

Thanks, Norm B