One potential concern would be the magnets used to hold the mat down onto the bottom of the tank....eg....with a stock poly tank...
I wonder if the magnets are strong enough to 'sense' the skid plate below the tank....doubt it....but...maybe some strong earth magnets placed on the outside of the tank to 'connect' with the internal magnets might work....
Kurt; but you can call me anything you want, except late for dinner
1988 Jeep Grand Wagoneer
Member, FSJ Prissy Restoration Association
Hand me that doo-hickey wrench thing, and a beer