I too have a DRW. I too have ripped them off on previous trucks by backing into a gravel pile or something similar. I am considering making my own, including the flap supports. I will probably use 1" square tubing and 1/2-inch thick horse stall mat. I will have to play with them a bit to see just how far back they need to be from the tires. Right now, I'm thinking a two piece flap. One piece above the supports and one below that will be hinged with pins. The lower will be designed to allow it to climb up on the tires. For this reason the length of the lower flap will be critical.
Wayne