My initial addressing of this problem worked reasonably well, but still had its drawbacks. I took out the tabletop, which allowed us to get up at night a little easier. Without the tabletop, we effectively had twin beds with an open aisle between where the table top had been. The beds were just a little narrow, however, so I added a wider piece of plywood to each wheel-well. The cushions required widening to match the wider bed base. I managed this by adding a length of large swimming "noodle" between the cushion and the wall. The large noodle was almost the exact diameter as the thickness of the cushion. We then laid a 2" thick memory foam mattress topper and there it was. Nice comfy twin beds. Well, mostly.
We used the new beds on our 46 day long trip out west in 2014 and again in 2015. But, there were still issues. The sections of cushions just didn't mate well with the folded down sofa and even with the memory foam topper, were a little uncomfortable. Then, getting up at night, the topper would tend to crawl off the edge of the bed. And there was the daily making of the bed at night and unmaking in the morning to raise the sofa back up. There had to be a better way...
I got this idea back last fall of removing the sofa-bed and building separate twin beds. It has been a slow project due to weather and lots of interruptions, but I'm getting there.
I started by removing the sofa. A few nuts and bolts, unplug a wiring cable and a few grunts (with help) and out it came. Then I removed the seat belts to clear the area better. And, in this photo, you see the partition I made which will establish the separation between the interior and the storage area accessible through the rear doors. Visible ahead of the partition are the wheel-wells mentioned previously. The photos below show the area behind the partition for rear-accessed storage.
One consideration I had was to make a storage area for my Tailgater Dish TV antenna (yes, we have satellite TV available on our trips). The Tailgater, although relatively small, presented a small problem in that it was a hair taller than the wheel-wells which set the level for the beds.
The photos above show the general size of the Tailgater and the box I made to store it in for our previous trips. This proved unsatisfactory because it made an uncomfortable seat for meals and sitting at the table. So, we put the original seat back in and I started castings about for a better way. The new bed construction opened a new possibility.
With the partition in place, I constructed two identical (almost) bases for the beds. They were constructed from 3/4" thick framing sandwiched by 1/8" plywood. That made them light and relatively stiff and strong. I still had to construct support in the rear (head of the bed) yet, but this photo shows how the beds fit in.
You'll also see a false floor section under the plastic storage box. The studs sticking up through the floor, which were used to bolt in the sofa and seat belts, presented some obstacles. I decided to make these false floors which would give me some storage for seldom used stuff (spare water hose, extension cord, etc.) underneath and a smooth surface above where the storage box and lawn chairs can slide in without obstruction.
I couldn't run the false floor all the way across the cargo section because it would be too low for the Tailgater to fit. So, I made it with a space between for the Tailgater.
I found the antenna was the shortest lying on its side and the tapered corners let it fit perfectly in the space between the beds and the false floors on each side.
That's about the extent of my progress to date. I have made a section to go between the bunks and form a cover which will convert into a seat when needed. And I have finished exposed surfaces with a cherry stain and polyurethane. Things are on hold while we wait on mattresses. Actually, mattress (singular). We gave Stephen a full-size inner spring mattress for his camp trailer and he is giving us his foam mattress that came in the trailer. The plan is to cut the foam mattress in two and make two mattresses for Pumpkin.
While building the beds, I kept in mind the possibility of reverting back some day if and when we decide to sell Pumpkin. Another owner might prefer the original set up. So, with a couple of small exceptions, I have not made structural changes and have built the entire thing to easily be disassembled and the sofa bed reinstalled. Assembly and disassembly are a lot like a Chinese puzzle, but it works.