It's an electric bass I successfully installed the wring harness. Everything works. No shorts, and it's relatively quiet. I don't think this is so much because of the humbucking mod. It's pretty much just as quiet in single-coil mode. I am guessing that is due to the fact that the pickup is shielded all the way round due to the lipstick tubes.
I wish I could tell you that the approach went without a hitch and that I have found the world's easiest way to install the wiring harness. It took around 2 hours, and I really feel there should be a simpler way.
One thing not to do. Don't run all the pull wires to the holes before you put the harness through the F-holes. The pull-wires got all tangled up with everything. Finally I figured out to pull all of the guiding wires back out of the holes and just do one at a time.
The thing I made to pull the jack through broke. Solder to thin wire just won't hold up to much pulling. I had better luck when I tied it on to the plug. That worked, but I had to be careful not to pull any harder than I needed to. Except on the very last pot that I pulled into place. That one I pulled too hard. I pulled the shrinkwrap off. Fortunately it was close enough that I was able to pull it up with a finger through the F-hole and some very thin needle-nose pliers.
It will take another week at least before I can do final sanding and polishing on the trim pieces that are all that's left to put in.
I may be able to put the time to good use. I have spent quite a while today adjusting and readjusting the bridge and the pickup height trying to get the action where it belongs without the E string hitting the neck pickup housing and without buzzing. I'll need at least a week to be sure things are as well adjusted as I can get them. Once the pickup covers go in, I won't be able to adjust the pickup height anymore, so a little time for experimentation can't hurt.
What worked the best with all the parts was run one pull wire to one component, get it through the hole and put a nut on it, and then repeating. It took a while. Although not an unqualified success, it still worked better than any other way I have done it.
I am very new to this fretless thing, but it's fun to play and sounds pretty good. Really nice to be able to play it again, and see why I thought it would be worth the trouble of refinishing ;-)