Then it was the thing about hooking everything up! This was really more difficult than I had imagined, but it all worked out well eventually!
I spent some time soldering and tinkering to get everything to connect properly, after I had made the remaining stretch sensors. It was kind of scary soldering stuff so close to the fabric, but no mishaps and everything flowed smoothly! Then I connected everything to a protoboard onto which I had attached the Teensy, and now I had the circuit in physical form!
It was really hard work, but now it's finished and it looks pretty much like a mess! Ideally the BBB would have been added here as well, but since it never arrived I never got the chance to add it