So a while ago I began this project, I couldn't fine an Onda Core, however I did manage to find both a Vibe and a Street (one slightly longer one shorter with fatter wheels). Crucially they both have axles that fit the spine perfectly.
I really wanted to make this project a success so have actually already printed maybe 80% of the parts, however I have struggles to understand the documentation, the electronics are a bit much for me and generally I think this is very much a project for somebody who is already an electronics whiz and who can figure out solutions for themselves.
I unfortunately am not, and I know the team are very occupied with making the Hyperboard and so don't have time to spoonfeed me.
If there is anybody who wants either of these great conditon but now very rare Onda boards for a Spine project, hit me up, same goes for the 3D printed stuff (most done on a UM2+ and there is more than in the photo)