What I ended up doing was TIGGING additional steel rod around the narrow bead...making it at least 1/4' wide. I then knocked the proud down with a hard sanding disk and marked it up with a wide tip sharpie. Then with a large file, I filed both flanges at the same time...that is, I kept the file in contact with both flanges at all time...and kept filing until all the sharpie mark was filed away. Should be nice and flat.
