Do you know a good route to chassis ground in the PS rear cargo area?
If you go under the vehicle is easiest to spot the "hole" to route wires to the cargo area from the engine bay.
The hole is just behind the 2nd row seating about 10" and about 12" in from the outside edge of the body. You can spot the grommet from under the vehicle easy.
If you have Cargo boxes it will come in about 2" under the cargo box edge closest tot he front of the vehicle.
There is also grounding bolt near that hole.
There is a place to ground near the hole, and it's also an easy spot to route power to the back cargo area.
I put a breaker on both ends of that 4 AWG you have running from the Aux battery to the Prion-TR. I used 2 AWG for less loss here.
FYI you can connect that solar MPPT up to the input of the Orion-TR and use that 4 AWG line as the feed back to your Aux Battery instead of running a 10 AWG that whole way. It is a long run to go from the solar MPPT all the way to the aux battery, and then all the way back to the Orion-TR vs just going directly to the Orion-TR.