I’m nearly ready to go ahead with the “final” set of wheels for Percy. These will feature a combination of keys and Loctite to ensure everything goes together in alignment and, more importantly, stays that way. The 3D printer makes test fits unusually easy, and so, I’ve broken from my damn-the-torpedoes tradition, and made a test fit of all the parts. Disassembling the drivers will destroy the centres, but, their replacement will be a simple matter.
Pembroke:87 
Looks robust. I forget what the two split axles are glued to and how alignment on that centre piece is locked?
The axle core is 1/16” steel. The key holds alignment with that core as well as the outer insulated tubes. Indeed that is the alignment that matters.