The classics say:
“Head upright to let the shen [spirit of vitality] rise to the top of the head. Don’t use Li [external strength], or the neck will be stiff and the qi [vital life energy] and blood cannot flow through. It is necessary to have a natural and lively feeling. If the spirit cannot reach the headtop, it cannot raise“. Actually, it’s a great description! But it begs the question, how should you position your neck … not just in Tai Chi, but in day-to-day use?