Too efficient or not efficient enough would seem to have a great bit of variance depending on where one lives, the type of driving and environmental conditions.
Putting an air deflector plate in colorado might be very different than in Las Vegas during the summer.
This seems to my uneducated brain like a very bad idea as a "fix."
2012 F150 Screw EB 5.5' 40/20/40 leather. Max Tow. Roll-n-lock, bedrug