I have tried to use those kinds of "cuffs" but they arent exactly practical cause they have sharp edges and all that but most of them are in stainless steel and therefore shouldnt cause allergic reactions but I know there are cheaper versions too.
I use another kind in my daily work and they are of a much nicer plastic lined kind which I guess would be better on the breast..
The upside is that it is very easy to get "just" the right pressure on the breasts but the downside is that if you aren´t careful you will cut the breast.. and I dont want that.

Rope is way nicer to use though and looks better although the metal "hose clamps" does have it´s benefits .