For what’s it worth, we have a Thule Evolution XL and have had this issue. I had the rear bar as far back as possible and tried to balance the load as much as possible but still had a tapping on the roof on our first and only trip with it. Had it on our 2008 XL Denali. My resolution was to again readjust the contents best I could and then I ended up buying some micro fiber towels and some gorilla tape at a Flying J and made a pad on the bottom at the rear of the carrier and that took care of the tapping sound. Haven’t had to use the carrier since so haven’t looked for a more permanent solution.