Late to the thread. Thanks for asking the question.
The only thing I'm perplexed about is that slowmover hasn't mentioned Dexter axles. ???
My residence is a 35ft R-license park model. I don't like 'tiny houses'. They tend to have bad proportions of the trim to the overall size. I once had a 1951 Silver Streak Clipper like this one:
The half-rounded top and ends is a good compromise for interior space vs aerodynamics. The limit for interior space would be as a U-Haul trailer. The limit for aerodynamics would be the Bolus
For ease of construction I would minimize the interior framing and go with a stressed skin pod:
Turn the Bolus around and follow the Aerodynamic Template and you get this:
Else the traditional shepherd's trailer
Just add a retractable boat tail:
I agree that Watt's four-bar linkage is magical, but I'd follow this:
A roof and three walls four-barred off a floor with three walls and a roof with a fold-down floor section.