Our Suncruiser had flip down cabinet doors on the dinette seat ends for storage. We made a canvas clothes bag to fit one and held it in with metal grommets and turn buttons.
While the space under the booth seats in this Sunstar is accessible from above by removing the cushions and plywood, that's not very convenient.
After a lot of exploration and thought, I figured out that at least one end was easily removable by removing 7 screws. I took it off, and marked and cut out an opening. The plug came out so cleanly that, with a little work, I probably could have used it for a flush door.) Then I made a door from birch. The partition is made of particle board, so I ripped 3/4" x 1/8" strips from a scrap of birch to line the cut hole edges.
I did goof up the detail on the door front that was supposed to echo the detail on the cabinets and drawers, but the door is far enough away from everything else it's not really obvious. (The detail was done with a molding head in my table saw.)
The strips and door were stained with my Varathane mix that matches Wiinebago's "Forest Cherry" pretty closely, and then covered with clear satin spray finish.
I wondered how to most easily find the drawer pulls and knobs that match the original hardware. Low and behold, molded into the casting for them, I found model numbers and a trademark. A quick search on-line, and a couple of clicks on Amazon, and I had matching pulls 2 days later.
Now we have a place to stuff our dirty clothes. I just need to get a bag made.
The other seat end has the propane leak detector on it. However, there is enough room that I think I can add a fairly big drawer to it for more storage.