Dolan Pre Cursa / PreCursa / Track Champion

Start small and work your way up to 6mm. The rear of the bridge needs to be 8mm if you want to use a brake with a recessed nut. The hard part is getting the drill in place as there's a big seat tube in the way...

yup, currently holding a recessed nut in my hand and staring at the rear bridge. the hole would wind up being at an angle for that recessed nut , unless a dremel or small hand held battery powered drill might get in there, but small battery powered drills often dont have much of the torque needed for dilling metal.

i could always do it by hand. if i start now, ill be finished for christmas....