im doing something similar at the moment on 7'8" bars. i had some tubing that was slightly larger than the handle bar tubing and i cut out about a 4cm length and then cut it in half. then i just drilled out the holes for the switches and then holes for the mounting screws and tapped the holes. it sits over more snug than the raised one in the picture above. the tubing is probably a little too thin so if i was to do it again i would double up the tubing, weld the seam and it would be sick.