Fantastic Voyage: Evolution - All Models Rigged

I am using 'rigged' as a loose term, as there is not much to be rigged for my characters. However, I have separated and creating an inside for the Russian doll who open or only turn the top half of their body. Meaning that I had to move the pivot point of the top half of the body, to the back edge in order to create a hinge like movement, when rotating upwards.