My 2013 Thor ACE 29.1 had about a one inch gap in the black rubber seal surrounding the windshield, at the top center. I presume that the rubber must have just shrunk over the years, in Southern California sun. Looking for a quick fix, I cut a piece to fit out of a used bicycle inner tube, and glued it in place using Loctite's 2-part Plastics Bonding System. Made a nice looking job that was pretty quick and easy. Apply the activator to both surfaces first, then put a few small drops of the glue onto the rubber seal, making sure to have a bit where it will hold each corner of the patch firmly in place. Place the patch and hold down for a minute, good-to-go. See photos.
https://drive.google.com/file/d/1a1A...ew?usp=sharing
https://drive.google.com/file/d/1q0y...ew?usp=sharing