I have started assembling the tentacle! After printing one of the vertebrae, I held it up to a puppet that it could be used for, and I found that the diameter of the vertebrae was too wide. So I reduced the diameter on the original model to 1.5 inches, reconverted it to metric and printed 12 vertebrae. For the tip, base and vertebrae 8 & 9, where the cable housing had to be inserted or the cables terminated, I had to adjust the design so that the holes were 4mm in diameter.
Each vertebrae holds onto the central speedometer cable using a 10/32 by 0.25″ set screw. I had the drill and tap each hole to be able to thread the set screws. I am now waiting for more set screws to arrive, then, I will be able to thread through the outer cables and hopefully this tentacle will start moving!