Fork-mount brake cable hanger won't fit on Crosscheck Fork
I'm trying to install a Tektro fork-mount cable hanger (1277A) onto my Surly Crosscheck (to deal with brake shudder). But neither of the two provided threaded sleeves fit through the rear hole on the fork. The rear hole is the same as the front, which the provided bolt has only very small clearance to, and which my 6mm allen wrench cannot fit into (the corners just hit). Note both the front and back fork holes are radially scalloped, to match the provided scalloped washers.
I read on a few other BF posts that the best options are (a) drilling the back of the fork to 8mm to accept the sleeve, or (b) get a longer bolt and a regular nut, and probably a nylock washer.
So I'm pretty intimidated by the thought of drilling my fork; I've never drilled metal before. I have no drill press, only a hand drill. And I don't have any metric bits, and the bits I have are pretty cheap. Does steel drill a lot easier than I think? Should I just go for it? Or am I likely to really ruin my fork by not drilling straight enough, or wobbling and not getting a clean hole, etc?