Many towed's do not properly lubricate an automatic tranny or a transfer case and will overheat if towed any distance (These vehicles should not be towed unless modified by something like a drive shaft disconnect, axel lock or lube pump. I've used the last 2)
I also used the KarGuard back when it was called an RV underskirt (That towed had the axel lock) no problems to speak of however A hole got wore into it.. Likely due to improper install by owner. (me)... I know it made a big difference in the amount of "Grit" on the towed after a long trip.