Aerodynamics of the front end of a travel trailer

Let's face it, they are designed to be occupied first, towed second, and manufactured at the lowest possible cost.

I think the belly pans are a help, although a headache for DIY types. Glad I don't have one:)

Based on what I see going on in the PU bed when towing the FW I think a cab-top deflector would be helpful. A ton of turbulence back there. PITA the rest of the time.

It all depends on what you do, if the extra manufactured expense vs the extra fuel mileage is a plus. For me, generally it is not.