He wouldn't even have to notch or drill. Go to a hardware store, get a 2 place plug similar to a 4 wire trailer plug, or even just use a 4 wire trailer plug. Wire it thru the brake light, having the wire exit the bottom of the CHMSL and leave a drip loop to keep water out, then wire the other end of the plug to the lightbar (measuring wire to make sure you cut it long enough. The flat 4 place wire should seal right up against the truck. Then, when needed, plug in the bar and magnet it down. Remove when stowed. If you still wanted to use the cig plug, you could buy another 4 wire plug and wire that onto the cig cord for use on another vehicle. That way, you'd have power, negative, and pattern (as I assume the pattern button is on the switch like so many other bars).