I think I'm right in saying (and I'm holding the fort here til someone better arrives) don't drill your frame. Just buy the appropriate brake with nut and bolt attachment as opposed to the Alan key - recessed nut system you describe.
@Wrongcog started
London Fixed Gear and Single-Speed is a community of predominantly fixed gear and single-speed cyclists in and around London, UK.
This site is supported almost exclusively by donations. Please consider donating a small amount regularly.
I think I'm right in saying (and I'm holding the fort here til someone better arrives) don't drill your frame. Just buy the appropriate brake with nut and bolt attachment as opposed to the Alan key - recessed nut system you describe.