Skeleton layout part 2

Since my intital post on skeleton layout I've figured out how to use Google Documents... so here is a basic biped skeleton:
Biped skeleton

Things of note:

• There are two stored poses on the skeleton for use with the Pose Manager tool - the model pose and T pose.
• It has two roll joints in the upper arm, two in the forearm and two in the upper leg. You can get away with a single roll joint in each area if you have to, but two is what I'd consider the minimum for nice twist deformation. If you want to implement stretchy limbs for a game engine (so no joint scaling, just rotate/translate) you need more. Anyway, I'll come to all of that over the coming posts.
• The root joint at world orgin is a requirement of the runtime animation system, so unless you're producing game assets you won't need it.
• COG (center of gravity) position overlaps with spine_01. The reasons for this will become clear when I post on spine control set up.
• The top of the legs have the same tY and tZ position as the COG joint, creating a T-bar configuration in the hips area. I'm a big fan of this kind of layout as it means you can rotate the COG of the character without legs raising off the floor. It's also the preferred layout if your skeleton is to be used for motion capture.
• Fingers are not fully articulated