It is my experience from treating many cases with RSI (a.o. with mobilization of inter vertebral joints and release of localized muscular tensions) that the role of the para vertebral (neck) musculature in RSI has generally been underestimated and overlooked on the expense of the shoulder muscles. It is my impression from clinical experience as well as some research, that forward deflected position of the head may be a greater culprit in RSI than generally recognized. That is the reason why I emphasize the importance of vertical head position.
Comment : I agree with your pragmatic approach – for example, people who wear bifocals may need a low monitor position in order to keep the neck vertical while viewing the screen through the lower half of their glasses. This is in agreement with the emphasis from Alexander teachers and AMT physiotherapists on the importance of re-educating and releasing the neck. In my own experience, neck/shoulder stiffness has had a direct effect on arm pain.