This method may OK for some electric brake controllers, but not for my 'proportional' Tekonsha Prodigy P3 as it needs to be mounted in a particular orientation to work properly. After being mounted it is also needs adjustment for gain and boost and if moved would need to be re-calibrated. It can also me unclipped from the mount in seconds and stored out of sight.I don't like to keep mine installed permanently for something used maybe 5% of the time. Also, don't want to create a target for thieves to slash the top.
Mine is installed with a RAM mount to my CMM grab handle mirror mount. I extended the brake controller wire harness up to the A-pillar behind the grab handles, and installed a waterproof four pin "aircraft" female socket in the plastic molding, and a male plug onto the rest of the wire harness to the brake controller. Installs in a few seconds when needed, and put away and locked up when not.