There's really no muscular advantage to doing a so-called full range pull-up. If the point of this exercise is to engage the back muscles (lats, teres, rhomboids), then what you want to do is concentrate on the motions that these muscles are designed for. Well, the lats and teres are designed to move the arm from shoulder flexion to shouler extension and from shoulder abduction to shoulder adduction. There's no advantage then to a full hang, since there's no resistance torque created in that position. Plus, there's the danger of letting the scapula retraction go there that can cause minor injuries.
I think the best pull-ups are from about 135 degrees to about 45 degrees, in other words, working around the 90 angle where the peak muscle torque takes place. It's also a good way to avoid those pesky aches and pains from pull ups. Just a suggestion.