[Big Dave]

I’ve thought about this – strictly for the 1-percentile that puts 25,000 miles a year on an RV (race crews, etc).

Using my truck as the tractor. Mine is lower than usual and only SRW, so the cab shows 79.9” wide and 72” above grade. At the top of the bed (48” above grade) it tapers in on a 34 degree angle to be only 48” wide at the top of the cab.

The Bowlus Road Chief was 80” wide (todays RVs are at least 96” wide).

Start with a 79” wide Hi-Lo design. (Using my truck’s dimensions) have its road operating height no more than 71”. In camp it deploys higher. Compensate for loss of space (by making it narrow) with some additional length. Taper it in at truck-cab angle at the top. Now nothing “shows” in the air stream – just a small step at the interface.

Given the cites posted by trebuchet, I wouldn’t go wild on the shape – just avoid the A/C tumor on top and round the edges a la Airstream.