I mentioned in another thread that there were only two ways to access the water heater bypass valves on my '86 Sovereign
25'. One is through the rear streetside storage compartment and the other is to move the mattress off the platform, unscrew about 8 screws then remove a 48" wide by 50.5" deep sheet of less than 1/4" board for valve access. Since I have to crawl through almost to my waist to reach both valves and almost got stuck around mid chest level all three times I have opened/closed them, I was tired of that. The second takes more time and is a pita especially if you don't have an electric drill/driver handy.
Since the wood was especially thin and the PO had put another 1/4" sheet of plywood and a rubber sheet on top to protect the mattress, I decided it was time for another project after finishing the installation of my third solar panel. I bought two sheets of 11/32" BC pine exterior plywood at Lowe's and received my 8" deck access hatch from Boater's World. First picture shows the mattress and plywood on the left and the existing thin sheet wood. The rest of the pictures show the sheets of plywood cut to 48" wide by 52.5" deep. My mattress is 53" deep by 75" wide and I wanted a deeper platform for more support near the edge of the mattress. They also show the boat deck screw-on hatch, plywood sheets after a coat of spar urethane both sides, hatch installed, plywood sheets installed and last picture showing access to both bypass valves through 8" hole. The hatch adds less than 1/4" above the plywood so I doubt I will even feel it. One picture in there shows an aluminum brace that Airstream did not feel the need to cut off to the correct length. I had to cut it back about 1/4" in order for the brace to drop past an aluminum rib just like the other braces. I can't believe someone wouldn't take the time to cut it back at the factory.