Not the shortest, but no 83-seat sea monster
I still need to get into a real bus with a measuring tape, but I'm hoping I can put a fairly narrow "head" back left (seat faces fore-and-aft), maybe next to an abandoned chair lift (if I'm lucky), slip in a wall, and lay a full size bed (also for-and-aft) next to the head.
No sink (use the "kitchen") and no shower (rig an outdoor camping shower outside the lift door or emergency exit.) The shower is enclosed, and it's only cold until you get dressed again. (Some call it invigorating.)
And, use the shower at the campsite, when I can.
Having the toilet near a door lets me empty the composting waste more easily every couple of weeks.
I'm thinking back and forth between a 39 seat and a 48, so sort-of-short and pretty-much-medium.
But no decision until I actually measure an actual bus.