I bought (2) rectangular plastic containers with snap-on lids at a discount store. I forget what size there are, but a rolled sleeping bag will just barely fit in  one. These containers are definitely not watertight, but I added foam weather-stripping gaskets to the lids, and mounted them (with ratchet-straps) just forward of the companionway bulkhead and to each side of the boat. The ratchet straps attach to "steamer trunk" handles (which fold down almost flush when not in use.) which are screwed into the butt-strap on the bottom. I keep clothes and a towel in the port one, and a sleeping bag and small pillow in the starboard one. All is wrapped in (2) layers of plastic "trash compactor" bags. When it is "beddy-by" time, I place the starboard box, emptied of it's sleeping bag, on top of the port box, leaving the starboard-side of the boat clear for sleeping (the mast step pertty-much ruins the port side for sleeping). When strapped down, the plastic boxes are about 3 inches inboard from the sides of the hull, so that if a little water gets into the cabin during a capsize, the boxes should be above it.

For storing food and cooking utensils, I added a little bulkhead less than a foot behind the stem, and which is fitted with two small shelves; the two shelves, along with the boat's bottom, provide (3) levels of storage for food and such. I found that I can squeeze about (3) days worth of canned goods in there. The openings through the bulkhead, to provide access to the shelves, were made small so that stuff would tend to stay inside during a capsize.

For "cold storage," I bought a 16 quart plastic cooler and arranged a hold-down-strap at the rear of the cockpit for it (the long tiller renders the rear of the cockpit mostly useless anyway.) The little cooler is tall enough to hold 2-liter soda bottles, which I fill with water and freeze to provide ice and fresh water. 

I could not find an air mattress that would handle the extremely narrow bow area, so I used (3) layers of 1/2" thick foam "hiker's" pads from Walmart. It is not thick enough, and I will need to add more foam. If necessary, the foam can be cut to fit the area at the bow- an air mattress can not. When not in use, the foam pads are held, upright, against the Port side of the cabin by a bungee cord and screw eyes. Also bungeed to the Port side is a first-aid kit. I also have holsters mounted at each end of the cabin for holding small "AA"-battery-size flashlights, and have a small compass, line knife, and am-fm radio mounted inside the companionway bulkhead. Something I always carry in my boats is a "head lamp," a flashlight that straps to one's head, also called a "miner's light" or sometimes called and "illegal dear-hunter's light." Very useful when you need your hands free. The headlight, flashlights, and radio all use the same size battery.

I slept with my head forward, which put my ears about even with the forward frame, with about 3 inches clearance between ear and frame. Jim suggested sleeping head-aft, which would put one's feet in the narrow area, but with the boat's rocker, that would also probably put one's head lower than ones feet, especially if the boat is drawn up on the bank.

I suppose a short person could sleep in the cockpit.

I wired the boat with running lights, (2) cabin lights, and a triple cigarette-lighter-outlet. The only item I carry which uses the outlets is a cheap hand-held spot light, which we used late Sat. night when seeking an anchorage after the "bull session." Everything is powered by a 15-dollar lawn tractor battery, mounted in a box located at the bottom-center of the companionway bulkhead, inside the cabin. The battery is inside the cabin to avoid drowning in the event of a capsize. The box is fastened down and the lid bolts-on with wing nuts.

I made a poly-tarp "slot cover" which is attached by snaps and supported by (3) wood bows with fit into slotted brackets- the bows are curved-up about 1 inch, but the cover still has "flat" areas. We had a fairly heavy 15 minute rain shower Sat. night and the cover handled that with no problems. the cover has (2) vertical "flaps" for covering the opening in the bulkhead- the outer one is polytarp, while the inner one is bug screening, to provide ventilation when the outer flap is rolled up. Or both flaps can be rolled up.

The mast must be unstepped for the cover. I have permanent crutches to hold it and the sprit. I did not see where it would be real practical to cover the slot while sailing, so I arranged all the stowage/ equipment to handle rain or spray that comes into the cabin area while the slot is open: for example, the previously-mentioned am/fm radio is of the type intended for use in a home shower; so it's supposed to be waterproof.

If I sit-up while seated on the cabin floor, my head is pushing up the slot cover; there is not full sitting headroom under the cabin 'roofs," unless one is reclining. 

I have a 15 lb anchor that bolts to the fore-deck, and a second 15 lb anchor bolted in the cockpit; neither will move in the event of a capsize. For the weekend, I carried a second anchor line hung on a utility hook in the cockpit- it would have been lost in a turn-over.

Fuel for the 1945 2 hp Neptune outboard consisted of a 1 1/2 gallon tank laying in the cockpit. I used less than a gallon over the whole weekend, despite quite a bit of motor'n.

Winds were light and "flukey" over the weekend, but the AF3 exhibited no bad habits under those conditions. In my search for cheap hardware to attach the sail to the mast, I ran across some dog collars that consisted of plastic webbing with a quick connect snap, a buckle for adjusting the length, and a sewn-in "D" ring. I bought a bunch of these, lashed the "D" rings to the sail's grommets, and have found that I can hoist or lower sail very fast, as I can quickly connect or disconnect the buckles.

Prior to launching the boat, I had not considered the oars to be a serious propulsion method for this boat, but after rowing it with my 8-foot oars, I have somewhat changed my mind as I was able to quickly get the boat up to hull speed, but am too "out-of-shape" to keep it there very long. 

All in all, I have been able to "set-up" the boat to store those items I thought would be useful to carry along, and to store them out-of-the-way, in a manner that would prevent their loss during a capsize. All the while keeping the boat's trim within acceptable limits.

I can see a few problem areas; for example, it is fairly easy to unpack and set up the foam pads and sleeping bag with the slot open, but to try to do it under the slot cover in the rain will entail much crawling around. I suppose it would be no worse than setting up a tent in the rain.

And although I brought along an extra plastic bucket for "emergencies," the AF3 cabin does not provide much privacy for that type of activity when surrounded by other boats.

I should add, however, that all last summer I carried a "porta-potty' aboard the AF4, which just barely has the room to use such a thing, but I have never used it, going ashore for heavy-duty business, and using the gunnel for lighter duty, after dark or in secluded areas. The porta-potty still smells factory-fresh.

Lastly, if i were going to do it again; i.e. build a 16 ft boat for day-sailing and overnighting, I might consider building the MayFly 16, instead, and sewing a poly-tarp boom tent for the cockpit. The Mayfly has covered storage fore and aft, and a centrally-located cockpit that makes it easy to keep the boat trimmed, and that cockpit, covered with a tent providing sitting headroom, would be plenty spacious for sleeping two, as long as it is not cluttered-up with
fixed seating.