I don't think you've got enough length on the part that attaches the shifter to the bar to do as you suggested above. You'll want to put the brake on the bar and then the shifter into the end of the bar. I think that sfclearwater was referring only to running the shifter cable through the base of the brake. Likely, you could run the shifter cable next to the brake and then under the bar tape, but the brake and shifter would have to be misaligned by a few degrees to get that to work.