Adjusting canti brakes is sometimes really hard. It is one of my least favorite jobs.
I do not have a great solution to your problem, but here are some crazy ideas:
-use a file to get rid of that rear lip, so you can set the brakes closer to the rim.
-install the pad backwards so that the lip is in front.
-set it up as is. go to the top of the mountain and ride down dragging the brakes the whole way. they will wear into the correct profile needed.
jim
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Cross Check Nexus7, IRO Mark V, Trek 620 Nexus7, Karate Monkey half fat, IRO Model 19 fixed, Amp Research B3, Surly 1x1 half fat fixed, and more...
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SB forever