I've noticed when I had a 300 2.8 IS and now 400 2.8 IS that the hood starts scratching the outer areas of the lens. It's the screw that mounts the hood onto the lens that is causing this. I believe it's a piece of metal that clamps onto the lens. Has anybody found a quick fix to this? I'm thinking of just putting gaffer tape on the clamp's surface but not sure how well it will hold on real active shooting.