I'm picking some up tonight for a trailer project...unfortunately, no matter what you do, they look stupid....
IMO, set them up as a receiver mount....1-1/4" small receivers into the frame at the back, flap hangs down from there, easy to remove for trail use.
Most any autodroid store has them in pairs for $15. Just add bracketry.
Also, check your DOT laws regarding flaps and such....you may find something about not required if the vehicle didn't come with it stock, or height issues, etc. Worth investigating before you slap something on there.