I've heard two major schools of thought on how to set your head height when in the locked in position:
A. Eyes even with the top of the batter's zone
B. Chin no lower than the top of F2's head
Sometimes these will be the same thing, but it depends on the height of the batter, F2's height and how he sets up (some set up very high while others set up very low). When I first started out, I used A, but I have been using B for a while now. Id' be curious to know how others set their head height when in their locked in position.