The shortest that comes to mind was a Fleetwood floorplan that put a queen crosways against the back wall. Left side and open. Model (Tioga and Jamboree) was a 26something for 27 foot length.
I don't know that it is an issue an owner can solve, if there is not enough room in a C this length for this kind of bedroom and still having living area up front. It usually takes a rear slideout, since a front slide only opens floor space in the living room.
You get closer in very short A's, which are coming back, because they can swivel front seats to use them in the living/dining layout.