[Beaver]

I have used a large Taylor Wing while hauling 3 different 5th wheel units. Current truck is the 08 F350 dually with 2wd with tow haul. I can tell you the following facts after hauling 1000's of miles
1. Mileage runs from 7.5 to 10+ running 60 to 65.
2. Does keep bugs off all but the upper area of the rig
3. My estimate of mileage gain would be no more that .05mpg
4. The one area it makes a huge difference is pulling into a head wind. It slices right through and keeps the mileage up.
5. Would you recover the purchase price. Probably not.
6. Key to the best gains is location on the truck, and the correct angle. If one had access to a wind tunnel I know the mpg gain would be much better.