Saw on a separate article that you’re enjoying making use of the space on top. I put a plastic lumber deck on the back 1/3rd of my International Harvester. Run two plastic lumber supports over the top of the rails, with risers on the rain gutters over the windows. Build up the frame and deck the full width of the bus! If your bus is built like mine was you don’t even compromise the integrity of the roof when you install. Relaxing in a folding chair on top of the bus at the end of the day is an experience beyond compare. Message me if you want to see a picture!