Kelly Starrett and Carl Paoli talk about the head position in the dip and its role in getting into good shoulder position with a stable, neutral thoracic spine.
Basically, you should be packing the neck just like in deadlifts.
What is packing the neck? Cervical retrusion with capital flexion.
Or as Charlie Weingroff said
“It basically looks like you are making an unattractive double chin and feeling a lot of pressure in the cervical spine.”
