Thought I'd pass along where I ended up installing a brake controller in my 2013. I won't need to do much towing - probably only a couple times a year, so I wanted to install the brake controller in a way that was least visible when not in use.
Basically, I installed the controller in the driver side left-hand coin tray that is also the removable fuse box access panel.
Only real work needed is to cut an opening in the bottom of the removable coin tray in which the controller cable will pass through.
Velcro tape was placed on the top/bottom of the inside of the coin tray and on the top/bottom of the controller.
Here are the photos. Feel free to ask any questions.