Hey! — Sorry about the link issue — currently working on a major revamp of the entire site and the forum should be working more smoothly in a couple of weeks —
That’s overall a very clever way to diagram the game, and I think it was very smart of you to infer that P and Q can’t ride together and to put them into separate cars — the only question I have is how you know O goes into the fourth car — I don’t think we can know that – I do think you can infer, per the way you diagrammed it, that either O or R has to go into the fourth car, and, as you said, since they can’t go together, T must go into that fourth car.
HTH and hope you are finding the Trainer useful — let me know if you need anything else —
Mike