Most of the rear skirt wear has been on the entrance and exits of driveways and ramps. There have been times where it crushed the skirts when I would back up into one of the parking curbs.
I've been talks with aerohead to maybe make an adjustable/motorized platform that you could raise at slow speeds and lower during cruising speeds. It might be possible to adapt an old window motor/mechanism and some creative engineering to perform this task. I would make a U frame and attach the extensions to the current side skirts with the pivot point near the rear axle. This isn't a high priority project at the moment but it will reside on the back burner fer the moment.