I didn't worry as much about body movement because the bed is bolted straight to the frame. I put an abrasion cover on the wire thru the bed, good heavy duty nylon stuff, and left some slack in the cable. Ultimately I'd like a battery in the bed but I'll still have to run a charging wire to it.
My original plan had been to go under the overhang of the tool box but it didn't quite fit with my box being inside the bed.
My original plan had been to go under the overhang of the tool box but it didn't quite fit with my box being inside the bed.

