I initially thought that you were asking for the rear cargo length as you were concerned about sleeping inside, that’s why I posted pictures of how I utilize it for camping.
I used to go solo when hunting. I can fit a Coleman cot with the last leg folded up and resting on the upright back seat.
I now use a RTT with my wife.
You can try this.....
https://www.ebay.com/itm/Folding-Pet-Pool-Swimming-Dog-Cat-Bathing-Tub-Bathtub-Shower-Wash-Pond-47-D-12-H/223247081712?epid=15026319887&hash=item33fa9020f0:g:ZEUAAOSwI01b97oK
Perhaps you can modify this.
https://www.ebay.com/itm/500lb-Big-Game-Hunting-Deer-Hoist-W-Winch-Lift-Swivel-Gambrel-Hitch-Mounted-360/303359663948?hash=item46a1a51f4c:g:eXgAAOSwJYVdyo3L
Just came back from a long thanksgiving road trip from Chicago to Hilton Heads in rain, sleet and light snow (2,000 miles). I'm quite happy with the spacers, it rides like stock. It did came from Russia. Got it from ebay.