don't know what gird is.
this is what the orthopedic told us when we strained the rotator cuff last fall:
a loose shoulder is one of the things that allows good pitchers to throw hard. loose is fast and you dance on the edge of too loose which causes injury and loose which allows the range of motion to throw hard.
whether or not it is a cause or effect is arguable. it is clear that the ability to do this is present in those who throw hard. that is why you must strengthen the muscles of the shoulder to maximum levels without tightening them, and when you reach levels of fatigue in the muscles you must stop immediately.
most gymnasts cannot normally do full splits, but over time doing an aggressive stretching program they can achieve full splits without injury.
in my opinion, externally rotating the arm until the forearm is horizontal is safe. if you cannot do this naturally, i think you need to stretch until you can maintain this level of flexibility, then agressively strengthen the little shoulder muscles. this much flexibility is consistently exhibited in hard throwing elite level pitchers.
however i am not a physical therapist or medical doctor. take it for what it is worth.
kind of like using the smith machine for squats and always doing squats on your heels.