Hank--
The RCA plugs do NOT factor in. I assume you have that audio/video amplifier with RCA connections for those cables mounted on the back wall of that compartment, as most units do, but it typically is unused and doesn't really do anything--I de-powered mine by removing the white power connection on the side to eliminate the parasitic drain from it.
That second cable that you describe coming "through the wood wall at the front" may be your coax feed running back to the bedroom TV connection--I understand that Phoenix ran that circuit regardless of whether the second bedroom TV option was installed in the RV or not. Mine has the circuit, and I don't have a second TV.
The second cable from my Winegard dish antenna that hooks to tuner 2 runs in parallel with the cable (with the tape) for tuner 1. In my installation, both exit from a hole in the back corner of that compartment, next to the Winegard antenna power switch. If I remember correctly (it's been several years), when I did my set-up I couldn't find the second cable either and Phoenix advised that it would be coiled up behind the wall or something--I may have had to remove the Winegard power switch plate to find it and pull it out. In any case, the second coax was there, and now exits from the same hole as the primary coax.
Mike