[Mike O]

The right elbow is always going to be touching the outside edge of another sphere made by the upper right arm around its center - the right shoulder. Whilst the shoulder may move to change the location of that sphere and relationship of its place in space per shoulder motions, the internal power package relationships cannot change.

So we have a whole construct of spheres now of the power package

The left shoulder - primary lever assembly
The left wrist - secondary lever assembly
The stationary post or point - either head or point between shoulders
The right upper arm - equi-distance either directly from the left (point between shoulders) or at opposite end of a chord from a radius (head).
The right wrist - working in conjunction with the left....

Oh and if your 'kuykendall' you may want to add the left elbow too...lol

If you look at the right arm structure - there is a basic geometry to it - if you draw a line directly from the hand to the right shoulder - the right elbow is always going to be halfway, forming an isosceles triangle on a plane. The obvious statement would be the closer the hand is moved towards the right shoulder the more the right elbow bends....

Matthew,
Not sure where your heading with your project or what you want to include- but sounds pretty good- you might want to consider including the sphere of the clavicle motion in your "equation", if you haven't already considered it.