Hi Mark-
Hatches are holding up great! I can stand on them, jump on them - they are solid. I used the Bristol 2-part finish over the Epiphanes wood finish gloss (really like the darker tone that varnish offers). Anyway, the bristol really seems to protect the varnish - I varnished the hatchboards w/o using the Bristol a couple of years ago, and pretty much need to redo those again. The main companionway hatch is also holding up great.
There are a few design modifications I would make to these hatches if I were to rebuild them again:
1) The rabbet supporting the lens was not wide enough - I routed 3/8" width, and would widen that to 3/4" width next time. You can see in the photo how close the fasteners are to edge of the lens. I had use #6's and they are still a bit too close for comfort to the edge of the rabbet.
2) Add a lower frame (much like Martin King's design) to create a seamless profile when the hatch is closed. Mine don't sit completely flush against coachroof, and could foresee a wave breaking over the bow getting under the lip of the hatch and carrying it off (That said, I think mine are still more secure than the original hatches).
Otherwise, I think the joinery, materials, etc are right in line.
Look forward to seeing your project! Good luck.