I studied aeronautical engineering at the school of big books.
While I commend the fine marketing and promotion of AirTabs, and truly promote capitalism, free enterprise, U.S.A. Manufacturing, and the free market economy, they only serve to reduce rear turbulence somewhat.
Air tabs do absolutely nothing to improve wind resistance. They will not improve the fact that you are pushing an approximately 110 sq.ft. wall directly into the wind every moment that you drive a motorhome.
If you can stand to look at them once they are installed, (and are capable of completely ignoring the laughter and stares that they cause to those that notice them and point when they pass or at the fuel stop), then they are great!