I have found something in the cr2 which might explain the asymetry problem.  The numbers for the mat spheres are all the same but reversed as you would expect. But the numbers for the angles are not the same only reversed, the numbers are actually different from side to side. They should not be since the rigg has been mirrored.  The angle settings being off could definitely cause differences in the way the mesh deforms.

Here is a pic of what I mean.  The angles are listed in a different order, this does not matter, but what does matter is that each angles counterpart from left to right should have the same numerical setting only reversed + or-. Thry are not the same, so obviously they are not getting mirrored correctly.

Edit:  This is the shoulder zrot (up-down)

. 

A HOMELAND FOR POSER FINALLY