Could the arm, hand & shoulder stuff be related to any repetitive motion, desk job, weightlifting? any past sport injuries, whiplash?
I know you said posture is good , no head forward of the body? no hunched or rolled forward shoulders? and no excessive" military" posture?
If a maybe for some of those - something from our TOS forum might fit or be helpful -
http://neurotalk.psychcentral.com/thread84.html