I have the same panel, and talked about it briefly in a video I did on my solar upgrade to our Milestone. If you look very closely you'll see the panel has more or less useless wiring and sizing (it's really just about good enough to maintain your battery in storage, so there's that). But the wiring through the roof is much larger, mine was 10GA and yours looks about the same.
The issue is, I tried to trace it and also tried to get Heartland to tell me the routing but both of those were no-go in my case. YMMV. The wiring coming into my PWM controller was more like 16GA so somewhere there must be a junction where they're splicing it. I could never find mine so I just ran a new wire with a new entry gland further forward, into the front closet in the master bedroom. It was easy to hide in there (I did it where the W/D would go) and run down to a frame rail and into the front storage compartment.