On a very old canopy I had I noticed the U channel had gotten a bit loose over time and since I didn't notice it right away it wore on the hole in the canopy a bit. I found some rubber to cut into a washer that I put under the metal fender washer that normally sits against the fiberglass and flew till I destroyed the canopy in a crash. On all my new canopies since I do the same thing with the rubber "washer" and feel it helps prolong the live of the canopy by preventing the metal from rubbing against it damping vibrations.