delamination issue on side of TT, need suggestions

Some deleted my comment so I will try this again. If your methods do not work then try using white eternal bond tape to cover the small area as I successfully did on a 12 inch cut in sidewall next to lower metal frame from road debris. Covered the hole nicely and no water leaks from wet payment. Tape comes in various widths and pliable and easy to use and last long time and blended in well with my white TT like yours. If desired you can spray paint over it. Tape is made for RV use. Good luck.