I do all my overhead pressing standing.
Used to do behind the necks....loved them. They just didn't have a carry over to my contest presses...all done clean and press from the front.
I press from the front, standing, bar from the bottom position. Standing it is HARD for me to get the bar to touch my clavicles and rest there but I go as low as possible. Contest rules state that it must go below the chin to count.
When I did behind the neck (love them) I went till the bar was at mid ear at least...