i wonder if that's one of those mysteries that never got cleared up in print, left/hand right hand not communicating, as far as gasket material is concerned silicon sealant was what some folks were talking about, i think neoprene would be neat as well, just make sure that the spacer and recessed lip are as neat and not wobbly. one of the reasons for making the recessed hatch is to use the same wood that the deck is made out of, so make the cut neat also. anyway just to repeat, 6oz laying up over the shear to shear strip as well as the underside of the deck is a very strong piece of wood.