To slow down process drill small holes from below up into the "patch", for lack of a better word, that you can see when looking from ground up. There is a material between patch and actual fender that is quite absorbant and retains water, if it is able to drain might slow it down. Mine are bad its 3rd on my list, I think I will get mine cut and patched up, I like the more traditional Tj look than flat fenders, I was quoted $130 from fabricator, he suggested flat style tube fenders since we were cutting. Probably cheaper all said and done than a new fender purchase install maybe, even if you do it yourself. Good luck.