Well it is official campers two tanks of gas later and the skirts are nothing more than French-Air-Brakes.
All on the same stretch of highway, all at 65 mph on cruise control
Previous high mpg 42.434 mpg (CDN)
With the French-Air-Brakes on 36.702 mpg (CDN) temperatures warmer air on all the way.
With French-Air-Brakes removed 40.055 mpg (CDN) even hotter temperatures and air on all the way.
Well that was a very interesting and counter productive experiment.
I will be skirtless from now on.