WOW! So many incredibly talented people gave me tips and...

No extra bones/drivers. This is mainly just better posing (twisting shoulder/arm) and weight painting!
Thanks for all the help, but still open to any suggestions! #blender #b3d

This looks fine when raising the arms to T Pose level, but raising them overhead always deforms incorrectly.
I'm not sure if it's the placement of the shoulder bones, the weight painting or the model! #blender #b3d