Thanks for the info, aero.
I'd say 71,000 lbs is pretty high---isn't 80,000 a typical top weight?
I looked around
Waggoners Trucking Home Page a bit, but I only found this confusing reference and inconclusive picture:
"... nose and rear bubble cones for added clearance and vehicle protection..."
(no mention of aerodynamics, but the photo of the blue tractor-trailer seems to show some kind of structure on there behind the rear corner of the trailer, but the photo's too small)
The Waggoners Trucking (Compay Info) [then click on "Equipment"]
I did notice Waggoners has a specialty of transporting wind turbine blades
btw: Did their drivers you talked to say that the boattails were a big headache at the loading dock? Could they feel a difference at 65 mph?