I think mine had piano hinges. I guess the wings were about 8" on each side. Your seat base can be used as a pattern. A lot of people use the back for the cushon if they are sleeping there so they don' have to mess with the bananna cushon. You can use EMT (conduit) for posts. The local hwd. store sell table leg caps to fit. You will need to weld brackets to the post to support/ attach to the upper bunk.