Thinking 3/8" because my cabin top is not one to stand on and no one would have to ever stand on the slider plus weight issues. I intend to build it flat.

Multi Craft Plastics in Tigard (now) only has 3/8" in clear. My large forehatch is white translucent acrylic. I can add a white solvent glued on film on the topside for about fifteen bucks, my installation. Or I can pungle up for white 1/2" acrylic.

Things to think about. Opinions greatly appreciated.

By the way, the slots in the sides of the rails are to receive filler pieces..mebbe today..and be routed off flush.