I’m not recalling having this much difficulty with this task on my ‘46. Lucky I guess?
I wonder if gently and slightly lifting the crimp all along one of the metal edges is an option? Both sides might need the same effort, but maybe try just one side first to see if it will be enough. Some sheet metal flat nose pliers carefully “walked” along the edge might do the trick. I’ve used that trick to open the door window scrape channels in order to remove the old rubber scrapes. The crimp was reestablished afterwards using the same sheet metal pliers and light taps with a hammer and blunt steel bar.
