Dan,
Asking RT to install dedicated wiring for future installation would help you a lot.
I am in the process of installing an LED headlight and port/starboard docking lights to the mast, as well as a hailer horn, on our R27-OB. Before starting this process, however, I had to remove and relocate the AIS 600 GPS antenna and the TV antenna, rerouting the wires to each, accordingly... and that's where my trial by fire started.
There are wire access holes in the cabin ceiling (above ceiling trim), and routing laterally to a sidewall (in our case the starboard side) and down into the cave, running forward to the dashboard / fuse panel. These wires are accessed in the wall thru the starboard port hole with trim removed. You might think so far, so good!
Wires are zip tied in bundles, and bundles are held in place to the adjacent surface with some pretty impressive tape. During fabrication, when all major components are exposed, it's easy to get to everything. Add the fact your not just an over zealous boat owner but a qualified technician, installation of electronic components and wiring is easy!
I will offer you best of luck, but more importantly wish you Godspeed and perseverance!
Bob
The Doghouse 2