#1 Do you guys do a pull-down behind the neck? and why? seems you would never pull something behind your neck naturally.http://tinyurl.com/os2pt
To do the behind-the-neck pulldown as normally instructed, you must externally rotate your shoulders as much as possible. This is a very delicate position for your shoulders.
The supporting muscles of the shoulders (known as the rotator cuff) are not in a good position to stabilize the joint and injury to those supporting muscles can result, which can lead to further injury in the connective tissue of the joint.
On top of that, since most people do not have enough shoulder flexibility to get a straight line of pull behind the neck, they must bend their neck forward to even do the movement. This can result in neck strain on top of shoulder strain.
#2 Do you guys do pull-downs using the palms facing you to work biceps secondary? Hows that working for you?
The biceps are often the weak link in compund pulling movements, especially if they are put at a mechanical disadvantage by a pronated (overhand) grip. The biceps are in a stronger position to flex the elbow when the palms are in a supinated (palms up) position. For some reason, people are loathe to exercise the biceps with compound movements. But I've had good results with reverse grip (and neutral grip) pulldowns and chins with regard to arm development