Watertight Hatch for Passagemaker Dinghy

We built our Passagemaker with the small (8"?) circular access hatches for the enclosed spaces in the bow and stern. The hatch in the stern went into the bulkhead as shown in the design. The forward one went in the forward seat on the centerline, since we have the take apart version. These are now used exclusively as inspection ports and ventilation of the enclosed spaces when the boat is stored out of the weather.

I've been contemplating putting in something larger, especially in the aft seat, to make it easier and quicker to store some of the many bits and bobs of gear I usually carry along, mostly in mesh bags clipped off to short jacklines I put in underneath the lips of the seats fore and aft.

The trouble is, all of this stuff has a way of getting underfoot in awkward ways, especially troublesom if I have a passenger along when sailing. One of these days I'm going to pitch my fool self overboard by stepping on something while changing position in the boat. I'd like to be able to store some of this gear out of the way while still having the watertight spaces intact to act as floatation which, from personal experience, is lifesaving in a capsize situation. It'd be nice to have some oblong, watertight hatches, easy to latch and unlatch, to get some of the clutter off of the floor and out from underfoot.

Have any of you ever done something like this with a Passagemaker Dinghy? Any suggestions as to brand, size, etc.? Installation tips? I have zero experience with this sort of thing, so I'm nervous about cutting large holes in my wonderful little sailing/rowing dinghy without some better idea of what I'm doing.

Any suggestions would be welcome. Any other tips for storing gear out of the way so it doesn't clutter up the floor? I will not be offended if you call me crazy for even contemplating such a thing, there already being sufficient grounds for folks calling my mental competence into question. <;-)

.....Gramps / Michael Scheibeck