I've finally made the Hackaday page for Spine. Here it is: https://hackaday.io/project/165110-spine-for-3pi
Parallel to working on the 3+Pi, Spine will be an optional unit for closed loop 3D space sensing. Ideally to be used with the 3+Pi, I plan on releasing the designs for anyone anywhere to use it.
Thanks, have a good day!