While the die set is a fabulous addition to any repair techs tool box, there is a cheaper solution. If you have a radius gage set the corners can be measured and then the specs can be brought to a machine shop and they can cut on a mill, a block that you can use like a dolly. Slide it in to the corner and a few taps should straight it out. You can also have the machine shop create a inner and outer die set too. This should be very cheap since it's not a very intricate cut. You can always have a set made when you need it rather than buy a 350$ tool you may use a half a dozen times, unless you can afford it...