John, can you post a picture of the top of your bus?
If I can get the hang of posting pictures, sure! However, I am photographically challenged at best. If you ever in SoCal, contact me and I'll give a free tour to whoever's interested!
Remember that I have a bus with a very curved roof, similar to the GMs and other older 1950s-era buses, so I can have the panels sit about 20 degrees below flat when thay're stowed for travel, or for when that side is facing a high summer sun. Folk with flat roofs will have an easier time of installing panels, but wiill lose the ability to have them much below level.
The walkway will be made from two 25 ft lengths of 2" 6061 angle bolted every 19" to the ribs, the 1/4" diamond-plate between them and 4" above the roof (to clear the junction boxes), and the panels hinged to the angle. Very simple really. I will include bracing to control any sideways or fore/aft movement, so the panels will be secure even in high winds when they're raised. The bolts will be socket-head 3/8" stainless, inserted up through the ceiling from below and going through each rib's flange, with EPDM gaskets and lots of caulk or butyl tape to stop water leaks.
At least, that's the plan!