Does anyone know of any morphs for v4's back? Like...vertebrae morphs for when she is very thin? or shoulder blades? something to make her back look...real?

If you load up the Stephanie Petite morphs, there are some morphs in that pack that help, a little bit, to address the issue. Morphs for the shoulder blades, to make them look like real shoulder blades, some shoulder morphs, lower back depth morphs, etc.. Don't forget about the Morph Tool, either. In a pinch, you can bring out some highlight morphs fairly easily. (ie: Emphasize the spine, for instance.)