We're getting there....
We used the same 1/2 inch scratch resistant polycarbonate sheeting for the companionway drop-in board as we had used on the pilothouse windows. It is nice crystal clear and durable stuff. Very happy with it, despite the price! The upright posts are 3/8 inch stainless barstock drilled with 1/4 inch holes and through bolted to matching uprights on the inside. I think it should work out nicely. The hatch itself is a Bomar aluminum hatch made just for companionways. We boughtt that from Henry along with the rest of the hatches he had purchased for the boat nearly 30 years ago.