The Submissive discussion

I'm looking for a book I have read, but can't remember the name of. It is similar to The Submissive series by Tara Sue Me, but isn't one of her books I have reread.

In the book, their is a Master/Sub couple. The sub is being trained by the Master, and sometimes/most times harshly. There is a scene where another couple visits, and the two women are placed with their heads below the floor, and the rest of their bodies above the floor. Their reactions are being watched via some sort of CCT.

There is a scene in the garage where the sub is bound, and possible water sports are taking place, but my memory is more foggy on that part.

Towards the end of the book, the Master wants the sub trained to be able to wear an arm binder and ballet boots, so he brings in another man to help the sub stretch and become more flexible, while also teaching her to walk in the ballet boots while her arms are in the arm binder.

I have looked through the many books I have read, but can't seem to find what I am looking for. I don't think this book is part of a series, but could very well be.

Any help in identfying this book would be greatly appreciated.

Did you find it ? I want to read it :)

Yes, sort of, but I think I have two books mixed together in my head.
The arm-binder story is Candace Blevin’s Safeword: Quinacridone. I actually like most of that series. Although I never finished the entire series, I liked the books I did read.