Have you had the fender all the way off or are you trying to simply squeeze urethane in there?Might help if you take the fender completely off and clean both surfaces really well. I even took a wire wheel to my support brackets to get a good clean metal to adhear to.Instead of clamps, I put all three of my trolling motor batteries on the fender to weigh it down and make contact while the glue dried.If it seems twisted, I wonder if one of the notches on the back side was cut just a little too small? might be something to look at. If it is, a cut off wheel works great to rough in a wider hole.