Originally Posted by
Velognome
Adjust the fenders using the stays. Heat guns and forcing plastic usually ends up just wrong. You may be too tight at the brake bridge to get a perfect fender line.
Correct! Don't try heating! Too much heat will concentrate at one point along the arc, and will collapse the fender. You'll end up with a sharp kink and warpage and you'll never return the fender line to a proper arc.
For plastic fenders, the only real option is using the stays and spacers at the frame attachment points to force a proper fender line under stress.