Thanks Alex. I think you’re exactly right, and I probably should have shared my thoughts a little more fully. This test wasn’t really indicative of any “normal” (hopefully) exposure to strong sunlight over a long period of time. Not very scientific, but interesting to see just how destructive the sunlight can be. However, even up close to where the clamp held it (severe discoloration from the rusting clamp), where exposure, if any, of the back face of the fabric was very limited, tear strength was severely reduced. The perceived tear strength was pretty much the same everywhere except for the area underneath the clamp.