HD,
The GS/100 method does work. It is the same method us pilots use to intercept a DME arc.
However being a good approach radar controller you would always put us on a 30deg leg before we join the centerline.
Perhaps the rule of thumb should be- if you have a guy 1.8nm from the centerline at 180Kt then it is tooo late for the 30 degree leg..........or if that guy is 1.5nm from the centerline then give a turn onto a heading that will capture from the other side along with something like "err not forgetting you just taking you through the loc for spacing err your number 1 report established"
Regards,
DFC