I had a discussion with someone at the boatyard on those. A new idea is using a fiberglass(or plastic) box beam of about 1" x 2" from McMaster Carr. The method is to slice a short side off leaving a 1x2" U channel. This is also done with bronze material on several boats I've seen(you can just see an example here on this Ted Hood Little Harbor.)

A good idea but there is a problem here(mentioned at the boatyard as well), that I have with the locker scuppers I have now on my boat: The channel is too narrow to get your finger in to keep it clear of junk that inevitably finds it's way in there. Mine are quite tedious to clear even with various tools.

I'm thinking of going with wood and making the channel wider for this reason(it will likely self clean if a minimum of 1/2" inside of channel). Plus, I need the structural support of a small 'beam' in my design. There's an area where coamings aft-narrow, and there is very little deck between the piano hinge and the coaming.

Once the bench top area of the cockpit is fastened to the coaming, it's not a support issue; but is a support issue, all through construction. The wooden scupper - a small U channel is a beam, and will supply support to that area, from below. Hard to explain,...

These scuppers are important. They need to be deep enough to actually work, wide enough to not clog up. I also have round scupper drains on bench tops which, while heeled under sail, drain the cockpit seats of spray and rain.

You can see the small bronze U channel mid cockpit here. My wooden channel will show as simply a small dark 'U' in the cockpit well on each end of the locker tops.