Played with elevator torque tubes, NC-2 inserts, NC-4 hinges, NC-7 jigs and hinge pins and took a long while to (hopefully) figger out how it all goes together.
Drilled rivet holes in the torque tubes, then match drilled NC-2 from outside the tube and deburred. Applied the plans grease then fixed the NC-2 in place with BSPQ-43 rivets.
Sealed join between edges of NC-2 and torque tubes with Supa Glue.