About to try this with a backpack attached to TT.
I am using raw colorful wires so orientation seems easy enough.
EDIT: I still got Ansible wrong. Double checked before powering on 
Can I use any row of 3 x pins on the backpack to connect any other unit or does the choice of row have any implications?
There’s mentioning of passthrough, the JF for instance has its rows marked as row 1 and 2. Are they interchangeable? (I’m connecting pin row 1 to some unspecified row of pins on the TT but worried about powering up yet)
EDIT: No problems with the above. 
Will raw wired fall out and cause trouble, like under transport? They seem very well fixed and the cable connectors are rather deep so I don’t believe they would.