One idea that I wanted to incorporate with a bulkhead hatch sometime is a quick-release system. You can buy quick-release bicycle seatpost bolts, about 1 1/2" long with a cam lever, at most bike shops and online bike parts sites. I was thinking about making a removeable bulkhead like the BBK ones, but cinching them tight with 2 of these seatpost quick-release bolts. They would draw on a couple of metal straps or wood supports just inside the opening on either side.

Dean