Made a Vertabra from the tail vertebra turned upside-down.
Placed them in a curve to act as placeholders
Adjusted the connection from the tail vertebra to allow for rotation along the spine axis.
Placed the finished vertebra in the spine. The spacing had to be adjusted to fit the connector.
Added "holes" in the pelvis to allow the spinal chains to terminate.
Added something for the arms and head to attach to.
To help tie the carapace and the chest armour together, added some "ribs", this also helps reinforce the skeletal aspect of the design.
Finally, added a plate behind the head to match the original description.