The front hatch is a 10" hexagon, but the rear one has been stretched to about 14" to allow larger bags/tent poles, etc. I installed only a plywood lip. I should have installed a spacer, because the cover won't sit down much farther than what you see here once the closure hardware is installed. After I paddle the boat for a while I may cut off the lip to the opening in the deck to make it a spacer, then install a new lip under it to make the hatch flush.

Dean