Paint Aero Shield with flexible paint of the same type used for Mustang bumper covers & Classic Side Pipe Covers. [The Aero Shield can be effectively integrated if it is two-toned to match the rear bumper insert. Consider low gloss black, like the GT series, for light colors, or light argent (silver) for dark colors.]
Your fuel gauge should read 1/8 or less. Gas is heavy; a light tank makes for an easier installation.
Raise car. The Aero Shield can be installed on a driveway apron, jack stands are better, a hoist is best.
Remove the two rear wheel/tire assemblies.
Remove the black vacuum formed plastic tub from under the fuel tank: