I just finished installing the 185W solar panel on the top of our teardrop trailer. Here is the set-up. There is an AGM battery in a battery box inside the tongue box and the Morningstar SunSaver MPPT controller is 3M VHB taped to the top of the battery box.
There is a Progressive Dynamics 45A control center/converter in the rear in the galley connected with 8ga wire to the battery. The solar panel (high voltage) is tied to the controller with about 14’ of 10 ga wire.
Nothing unusual until you want to use the load feature of the controller which would be using the 8ga wire from the PD converter.
The only solution I can think of would be to wire in a relay or use jumpers and I am not sure of how to go about that so I do not toast the controller.
The goal is to monitor the 12V load.