All of the hatch floors (well all but 1 that I now have other plans for) are glued into the hull and glassed. The forward ones provide a platform to stand on while fitting the forebeam to the boat.

I have also checked the level of the hulls. I have a mark on each hull at Waterline +1200mm. I set up the clear water level hose on each hull and found that the port hull water level is just above the line and the starboard hull just below. So over the 7000mm beam the boat is maybe 2mm higher on one side than the other. The WL1200 lines are take off the waterline marks and all of the marks are in thick black felt pen of 1mm wide so given that much margin of error (2mm each hull just in the thickness of the felt pen marks) I am happy to pronounce the hulls exactly level.