Paul, thanks again for the good information and tips!
An endoscope would be nice, and it doesn’t seem to be that expensive, which is really surprising! It would make things a lot easier. I already have a brand new, fairly big Hobie rectangular hatch installed, so accessibility inside to the hull is pretty good. Since I’ll probably be using that cargo space quite a lot, an electrical conduit would definitely be a good and necessary protection for the wires.
Although I’d like to avoid the boat turning into Emmental cheese, it might be necessary to install another small inspection hatch on the inside of the hull to lure the wire out.
But let’s see. Maybe it would be best to sail one trip first, keeping the power box in the open air, before doing any bigger crafts.