Can you post your success/failures of running wiring through here if you get a chance? I tried doing this last year and ran out of time and patience.
It was tight and took some time and patience for sure. There are I believe 2 x 1" conduits crossing beam-wise, only about 2-2-1/2ft long (presumably to keep wires isolated against bilge water?) I ran a few things through there at different times but the main ones were a pair of AC wires from the breaker panel to my inverter/charger under the sink.
I don't have photos of this, it would not look like much. I believe I used a coat-hanger to first push through the conduit, then attached an end of my wires, then pulled it through. Probably sprayed some soapy water on it as well for lube. That's about it. Good luck! At this point my conduits are FULL. :)