I didn't use either arm. The charger is connected directly to the ball on the offroam mount. I wanted to keep it as low profile and unobtrusive as possible. I can get a picture for you sometime this weekend. This is the base.
You should really look at a Tazer JL Lite. It's going to be the most cost effective way to, at a minimum, disable auto start/stop and program for the larger tires you're looking to install.