I think that there are a little mistake in the desgin of the cr2 of Victoria 3. I think that the breast are a mobile part as the arm or the legs. I think that the breasts must have a bone as the other parts of the body. Th morphs for the breast are insufficients, we need bend and twist !

Base Figure does not have all the morphs. You need Body Morphs for that. Also, what you might be experiencing is Kinematics. Some people like the results better with these off. Also, try using the Dials to adjust instead of using the figure itself. I find that gives more control without affecting parts I have no desire to affect.

No one can twist there breasts, remember it would be the whole area that would twist.

If you have a good understanding of Poser's Setup Room and Joint Editor tools, you can add bones to make the breasts posable. I'm not sure how well it'd work with Victoria 3's chest/collar grouping, however. It might be more effective on Victoria 1-2.

Of course, if you did add such bones to Victoria, you'd also have to add them to her clothing. Unless you were only planning to do nude portraits.

I think Magnets for this might work better.

True. And you'd be able to span the effect across multiple body parts (collar and chest) with magnets, unlike body handles.

You can also convert Magnets into Morphs for use with other characters once you have the range set up. I know some of the Props that affect specific Body Parts make use of this technique to create the Morphs.

Supermodel Vickie has breast parts, so does the GIRL, BTW, but SMV's also scale, I must have outdone DAZ on that one. ;-) The way V3 is cut up though makes it difficult to put in "ghost" breasts that work well, and if she was recut none of the existing morphs would work.