Ack! Fortunately, I had bought a brand-new 12-string Shubb capo when I was at Guitar Works picking up my new guitar, because I'd been acutely aware of the fact that there was no capo in the 12-string's case. There might have been an appropriate capo around somewhere, but it would have been a hunt. So Gretchen went upstairs and grabbed the new capo, I put it on, adjusted it, and retuned the guitar with the capo on.
And it all sounds just fine. Phew.
One song to go, but I wasn't going to try to essay Falling Toward Orion on the 12-string at 9:30 PM after a full day of guitar playing. Tomorrow will be fine.