Consider connecting the solar charge controller at the battery itself. Then you don't have to make any penetrations into the trailer, and you can mount the SAE connector to the battery box.
Also, the fuse for the controller should go at the battery end of that cable, not the controller end. Fuses are there to protect against damage from short circuits. The source of current that could cause damage if the cable gets shorted is the battery, not the controller or solar modules. Solar modules are self limited in current output, if you short them out nothing happens. If you short out the battery you get a meltdown. For the same reason, you don't need a fuse on the solar module side of the controller.