I guess you would use a dremel tool or a sanding block to chamfer the edges?
I'm going to try that on my '73 tii. I rebuilt the brakes on both of my tiis recently using the same setup. New BMW rotors, rebuilt calipers, Hawk HPS pads, Ate grease, new shims and the '73 has always squealed, but the '74 never has. I was careful and followed the recommended way of breaking in the pads that was mentioned here and on the Hawk pad box on both cars. '73 squeals and it pisses me off,
John