Thanks for the response, Paul. It's first scenario here - I'm adding them for volume/floatation reasons, and I agree that won't require much strength. My concern was that with the bulkhead hatch, I might get enough deflection/warpage to lose the seal. Wouldn't be catastrophic, but everyone likes dry compartments. The ring (bulkhead proper) is about 1" wide, and out of the boat it's pretty flexible. Once glued in, it should be stiff enough. The hatch portion has some flex, but now that I've played with it, I don't think it'll be a problem.