Like most cruisers, we needed more storage. We tried to locate any unused space on the boat and convert it to storage of some sort. One place we discovered was under the floorboards.
Under the floor on either side of the bilge is an area about 8" deep, the width from the bilge to the settees, and totally inaccessable. A little investigation showed us it was not a critical strength problem to cut into it. The hull is cast, then the inner part of the boat, the floors and the settees. It rests over the hull, but is not attached except at the sides and inside the bilge. The cross braces that are in the bilge, the ones that sort of divide it into compartments, are glased in inside the bilge, but where they extend outside the bilge, they simply strengthen the floor, but are not attached to the hull.
We sawed a rectangular hole in the floor about 2" from the bilge opening, 2" from the fiberglass settee, and on either end. The end to the rear of the boat was a few inches forward of the end of the settee where the nav desk is, the forward end was about 6inches from the door to the head. I made this into two pieces, so there are two openings.
This leaves a nice cavity, but there are a few more steps to do. First, you need a lip for those lids (old pieces of the floor) to sit on. Then, you'll find the edge of the floor next to the settee is a bit flimsy.
I solved the flimsy part by cutting a plywood stringer and glassing it in between the floor and the hull. Just lay it up pretty heavy on both sides and it'll strengthen it right up. Since it's inside a locker, it doesn't even have to be real pretty. Next, make a strip of good wood to go down both long sides. Drill some holes to screw it to the underside of the floor, leaving about an inch revealed to hold the floor pieces. Test fit them, then remove them. Glass them real heavy, a layer of cloth on the top and bottom of the strip, leaving enough to make a solid layer on down and turning onto the hull. Put them in place, drive the screws in, holding the whole mess in place. Smooth out the glass on the back sides and down to the hull, leave the edges stick out into the opening. You can trim it after it's cured.
Now that you have a lip, you still need to trim that glass back to the wood strips. You also have to trim the bottom edges of the panals you cut out to make the thicknes uniform. When they were laid up, the thickness varied quite a bit, they now won't lay flat. (Hunter probably never expected anyone to cut up their boats!) You'll also have to smooth up that lip and spend a little time getting everything to fit so the edges line up and so they don't rock when you walk on them.
If you got this far, here's a tip on how to do that. Get them to fit as well as you can, making sure that the panals are at least as low as the floor. Once they fit so that the whole panal is at or below the level of the floor, make some little wedges or what ever is handy, fit them so the panal will rest on them, and be flush with the floor. Then get some resin, some thickener and some wax paper. Mix up a real thick paste with the resin. Spread some all the way around the lip, then lay wax paper over it. Lay the panel where it goes, then press it down until it is exactly flush with the floor. Walk away until it cures. Then go back, remove the panels and grind the excess resin off that squeezed out.
I gelcoated the inside of the locker to make it look a little better. You might wonder if it's worth it. I now carry a cast 35 lb. Danforth in there, about 100 lbs. of stainless plate and other repair materials, about 50' of chain and over 300' of 3/4" anchor line. It gets those heavy items down low where they belong.
I'll try to add pictures soon.