I bought a bag of 60 BAC standoffs on Ebay for securing the Adel clamps throughout the airframe. Tonight I riveted two of them to the tailcone and bolted Adel clamps to them to secure the tail nav/strobe and pitch trim wires in place. They work and only require 1/8 holes in the longerons rather than a #12 hole for the bolt.
The second picture below shows how close the wires are to the middle aft longeron. I plan to reroute them so that they penetrate the bulkhead at a lower point so they exit just below the longeron.
Nav/Strobe and pitch trim wires secured to upper longeron