Please also bear in mind that the balance of muscles around the shoulder girdle, ie the tension of the anterior vs posterior muscles, affects the position of the scapula and the clavicle, which may narrow the costoclavicular interval (the space between the rib and the clavicle). So relaxing the pec minor, which can be done in a number of ways, may widen the space and relieve compression on the brachial plexus.