I like your "from the hip" thoughts. A single wheel "tail"(ala Burt Munro) definitely could add a dimension to the Moby theme.
Your careful nature(scaredy-cat) offers me confidence in bouncing ideas off ALL this group.
Last thing I want is for anything to fall off Moby at 55mph.
I will control my view of the iRV2 Forum on aerodynamics. drafting semis? yikes.
A boat-tail: Would a streamlined/narrowing extended "kammback" along the top w/long triangular "gussets" to the bottom of each side, be the reasonable starting point...to provide hinge points for the boatail sides to fold under? or support a flexible gap filler for a trailer?
A trailer option: I know other MH owners tow another car or enclosed trailer behind them. Some are sooo long, I think they're just showing off. A not too heavy single axle "GolfCart" trailer (10-12') was what came to my mind, with a kind of clam shell hinged enclosure for the just right (Bezier curve) shape. The challenge is the gap between the trailer & Moby. correct?
Moby is 11' tall & 8+' wide, "use its width as your reference for the streamlining, rather than the roofline". So the truncated end would be short- vertically, wide- horizontally? or tall- vertically, narrow horizontally? or proportionally rectangular?...lower vertically than center.