Just checked in with Stephanie and all went well yesterday. Macho was not weighed at the counter. The TSA inspector asked how much he weighed, however, and they said 16 pounds. Then he asked if Macho bites, and they said no.
The carrier didn't really fit under the seat, but Stephanie and Danny had three seats to themselves (aisle and window) and no one came for the middle seat so the flight attendant let them put the carrier on the floor. Macho was quite anxious to get out of the carrier, and the flight was actually early.
So all is well with one exception: Macho won't come out from under the bed. I guess it will take a while for him to appreciate his new digs. And Stephanie was off to the grocery store.