Palms outward, I can feel the strain developing in my shoulders when I raise my arms. It's easier to turn the palms inward. And one problem with Poser is that something like twisting your wrist produces skin shifts all the way up to your elbow. Some of the extra bones in Poser are there to deal with skin and muscle, not skeleton. I've seen examples of rigging for other programs which use extra bones which are not part of the normal skeletal chain, and moved by ERC-like methods. You have a buttock, sticking out at the back, but the thighbone is still connected to the hipbone. Unfortunately, the way Poser handles mesh groups I think you might have to do some strange things to make this work. Maybe something like a body-handle? Isn't there some figure which uses that for the breasts?