Done and done!!!
I ended up tying the model to the swivel chair in the room around her waist, then tying her feet by the ankles to the corner of the table-desk in the room.
After all the work tying her to the chair, I wonder if I should have even bothered, as with her ankles tied to a table she wasn't going anywhere anyway, and I was reviewing the clips and you can't see the rope around her waist anyway! (Well, you can in a few of them I think.)
I tied the bottom of the ankle rope to the desk and was just able to leave it there for all four models. Then she would just slip her feet through the hole, and I would move her feet up to the tabletop and she was trapped. It's funny -- one of my models, Pamela, is a TV presenter in New York and she was involved in this gig. Her feet are size 11, and they were so big we had to struggle to get them through the hole even when the rope was down and the hole was open!
She was embarrassed as she's a little ashamed of the size of her feet (they're huge, I think she fibs about size 11, I think they are at least a 12). But that was nothing, because once she was tied in the chair, my devilish tickler, Scarlett, began relentlessly mocking the size of her feet as she tickled. I didn't know if I should go forward as I know Pamela is sensitive about that subject, but time was tight and I had told Pamela that Scarlett was going to be devliish so I thought it would be ok.
I put a piece of sports tape over the mouth of each model, but I didn't like the way it looked, I thought it was kind of creepy actually. So I then tied a towel or a scarf over her mouth to hide it. Only one of my models, Chloe, didn't want the tape. She agreed to be gagged by a scarf, with her mouth open so that she could not talk.
Will probably put the first one up on my store in the next few days. Thanks again for all the help!