Quote - Hi Erogenesis, I am late seeing this message thread, so, my comment maybe already covered off.

You asked about extra bones, and suggested the abdomen area. Yes, yes please.

We use Poser & Daz for illustration and training in sport - artistic ones such as Gymnastics and others where body and limb movement at critical stages of a movement, are needed accurately - polevault, high jump etc, showing how the bulk of the body shifts weight around its CoG to achieve movement progression. The points of bend, and shape of back, are critical

We have great problems getting figures to bend correctly because they are missing pivot points in a bend from hip to neck. Now, if you could put one for each vertebrae, or each pair, we would really have something behaving naturally.

 

ok so from what I make out of your post is that the back is most critical, right?

One thing I need to research is by much does the chest actually bend? Because I have the feeling that the chest vertabrae don't do much because the ribcage holds it in place, correct? So Am I correct in saying that most of the bending comes fromthe vertabrae between the hips and the ribcage? and how deep are these pivots from the surface? Like 5cm into the body?

Ribcage depressions for CPR would be a speciality addon, but not hard to make.

"The fool is not the one that does something foolish, but the one that does nothing at all."