The edge should form a straight line together with the sword so that you can see all the stillness and movement of the sword and of the adversary. In this fashion you will immediately recognize what needs to be defended and what can be attacked. When seeking measure the head is on the left shoulder, when attacking the head is on the right shoulder and a little bit to one side or the other to be better guarded by the hilt. Or in other words, have your head back as much as possible while seeking measure and as forward as possible when striking.
For the replacements and movements of the head, often made while passing or voiding, are frowned upon by Capoferro.