Lance,
You probably know that one consideration is to minimize distance between the controller and the batteries. On my 2019, Phoenix mounted the controller inside the under-sink cabinet on the LH end wall; it is covered with a small removable panel. That places it essentially on the back side of the wall to your left as you enter the coach door. I believe that Jatrax (2017 2552) has mentioned in previous posts that Phoenix mounted his external control/display for his Samlex controller on the exterior of that wall (adjacent to the steps--next to the battery disconnect). In my 2019, they installed the Trimetric SC-2030 controller from Bogart Engineering, so since I have the TM-2030 Battery Monitor, that controller corresponds with that monitor for the read-outs, which is installed with the other data readouts on the wall behind the driver's seat.
Mike
