I think I have figured out a way to preserve what is left of my cracked plastic sliding door rail from completely becoming unusable on my '07 2100. Like everyone else, the rail seems to stick up a little too high and is easy to crack when stepped on. I devised a way to minimize the pressure put on the track when entering and exiting the RV. I had a piece of 1" x 1" plastic purchased from Home Depot to cover the bottom of a sliding door I have going to my outside deck. I cut a piece about 23" long, drilled counter-sunk holes and used self tapping screws to secure it directly to the front side of the bottom sill. NOTE: In order for the door to still slide across the rail, I needed to shave the front bottom edge of the screen door in order for it to clear the the new plastic piece. Simple Dremmel work made the job quick and easy.
I then took a piece of plastic carpet molding I had saved and used it on top of the metal strip and as close as I could get it just behind the rail. Now when I step on the rail, it is protected front and back from further cracking. Also, there is no impediment to the free movement of the sliding door. Since the rail seems to be irreplacable, this may prevent further damage. See attached picture.
