Worry not :-). I'm using the brackets as a jig in the way you describe, I even splashed out and bought myself some transfer punches to help.

Neil, I'm going to be bold and say I don't need any more brackets. If I do manage to screw it up I'd probably need a whole new set anyway. My attempt to cut a bracket by hand for testing makes me even more grateful than I was before for your help, I damn near broke sweat :-).