Wiring loom for C Shadow
I'm at this moment doing the same on my C Shadow. I'm using split-wrap from vehicle wiring products, which is flexible and accomodates ups and downs. It means I can construct the loom and test it BEFORE putting the sheathing on. It also accomodates leads forgotten despite all the care taken......
All the wiring from the back of the bike (stop/tail/horn/alton/electric start) joins the main sheathed loom at the rear of the UFM via an ignition switch under the battery tray. (The "tributaries" use smaller diameter split-wrap.) My main loom then goes up the drive side of the UFM, kept up out of sight by tie-wraps, and exits from under the tank above the tank mounting bolt whence into the headlamp. Wires are "diverted" from the main loom to the earth screw on the UFM, and to the electric start - an advantage of split-wrap is that everything doesn't have to be planned to within 0.001" in advance.
You can get a pretty good idea of the layout from Richardson, Chapter IX, page 120 where he gives dimensions of the wires and sheathing on the original.