[WildJohn]

although I see the obvious advantages to your design, (i wuld like to see a pic with it closed thugh) My neighbor used a technique that I liked so well I copied it on my next day off... and since then My DW and I have not had the knee pain we have experienced for the last year of full timing.. didn't make the relationship until the pain was gone suddenly..
I can take some pics and post them but here is the short story.. Went to LOWES and bought two five step risers/stringers, and some 5/4 decking material, a 24" square piece of 3/4" exterior plywood, and a box of deck screws... I had them cut the decking into 2' lengths. I screwed the decking on the vertical portion of the risers first and then screwed on the tread surfaces.. leaned them up against the extended original steps and adjusted them until the top step of my new staricase was even with the top step of the origiinal and screwed the plywood to the tread. then I took two of the pieces of decking and stood then on edge perpindicular to the length of the RV and slid them on top of the second step and screwed them to the riser. The height was a little off so I put a pallot on the ground and screwed the bottom of the risers to it and covered it with steping stones, it makes a little porch at the bottom and the 2'x2' plywood on the top makes a pretty neat little platform too.. With a little paint it will look pretty good and feels great. Now I need to get home and get a length of wrought iron railing I know I have lying around. total cost less than fifty dollars and less than an hour to assemble...
When we move I can take the four toenail screws out at the bottom and slide it off the foldable steps and it will go through the door to ride just inside I hope.. haven't tried but it measures out ok..
The reason for the knee pain became obvious once I started to measure.. check out the carpenter's standard rise for stairs and measure ours... one and a half times standard is enough to kill your knees.
happy camping
John