Nice to hear they worked out well for you, also cool that you went old school w/ the tried & true string alignment method, hats off for that.

Should be a viable option for those wanting proper camber w/ a mild to mid drop spring set.

What did you end up using to elongate the slots?

 

I used one of these - Oval/egg Double Cut Carbide Burr:

http://www.mcmaster.com/#rotary-deburring-tools/=ursm9t

I did the whole thing at a friend's metalworking shop, so he had air tools and already had a set of burrs. It was in a 90 degree pneumatic grinder. It doesn't need to be spun at any particular RPM to work, so one could probably find a carbide burr that could fit in a drill if they didn't have air.