I looked at a NIB flap. They have a black wear surface that appears to be glued to the bottom of the rear edge of the flap. The issue I have is this needs to be on the inside edge of both flaps to come into contact with the top mechanism. But thanks for the info, it suggests adding a wear surface to the bottom inside edge may be a viable solution. I am seeing the beginning of chipping where the top comes into contact with the flap that I want to prevent in future.