Now take no offense as I am going to be humorous here.
My bed supports are 2 one half inch X 54”X26” pieces of plywood on edge and attached to the wheel wells with bolts/rivnuts. Thats it! They also form two cabinets fore of the wheel wells and storage behind. Your steel framing bed support is as different from mine as any two minds could devise. Either I’m nutz or you are, probably me. But in my defense it has worked super well to both support the bed, allow it to collapse into a single bed/couch and has withstood every possible road condition/panic stop and has provided countless nights of bed comfort as a double bed and many nights as a single.
You certainly build a skookum van conversion! I like the idea it comes out easily too. Have fun!