[Dan in Pasadena]

Man, on that third picture, how did you open that thing up? With your teeth! Kidding of course. Are you thinking of cutting off that crimped portion? If so, you'll need a pneumatic cut off wheel - should be able to rent one if you don't have access. While you're doing it, why not trim up that cut out. You're planning on welding the whole thing shut again, right?