I thought I'd give Dan Ebbert's IK rig a go... Having a problem with it though.. When I adjust the Arm's Effector, the Wrist isn't staying in the same position as the effector, even though it's within the limit (not stretched). It's close, but not aligned. Perhaps a rounding error?
Shoulder: cw=true, upper=true
Forearm: cw=true, upper=false
No clue. Never tried it and I honestly would approach the matter differently these days. Maybe copy this to the Expressions forum or ask on AEnhancers. Dan hangs out there on occasion and surely will provide you with some clues.