This is what we came up with in our '74 Sovereign
. The space does not convert into a bed, we had that in our '64 Overlander and got tired of changing it back and forth so for this trailer we incorporated enough sleeping for 6 in the rear and had a dedicated dining area. This table is comfortable for 6 adults, and you could fit 8 or 9 if need be.
The table has a core of pine and resin impregnated honeycomb cardboard. Benches were framed with 2x2s with 1/8" Baltic Birch plywood fronts. Here's a photo with the table removed. The panel under the front bench is held in place with a magnet for easy access to that space for things not often used. There's also access to the umbilical wire connections. The strips on the front of the plywood were added recently to try to minimize the scuff marks from shoes.
Next photo shows the swing-out drawer under the street side bench. It pivots on hinges at one end and runs on a couple of ball casters across the front.
The balls run on strips of aluminum on the bottom of the drawer to prevent the plywood bottom from wearing. We usually keep folding chairs in here.
Long drawers under the curb side bench are easily accessible from outside.
Initially I attached the vinyl to the back of the seats, but had trouble getting them tight against the "deck" behind the benches. Recently I redid them with strips of wood to hold them down. Not the most elegant solution but cheap and easy. I'm sure a professional upholsterer would be able to do better!
We took a month-long trip with the table in place but without the laminate on it as the laminate had been ordered but didn't come in on time. This turned out to be a blessing in disguise as we found that the table was about 2" too big in each direction. It was hard to know this until we'd used it for a few weeks. I was able to easily cut it down since the laminate was not yet installed. The other good thing about all this was that Lowes didn't charge for the laminate because they messed up the order.