Use headshot=57 instead of headshot=1 and go from there up or down with the value to adjust it to what you need.
I think headshot=1 turns it on to the default of 55 or 57, I forget which but that value is the height adjustment for the headshot.
Try like headshot=65 for your tall model and see the difference when you shoot it.
I may have the numbers wrong since I couldn't remember the default value, because this is what Nickydude's Community Guide says...
Quote: "
HEADSHOT=X
Where 0 is immune, 1 is default, and any other value equals custom headshot height. We found that the default was a little low, about from the upper chest up on some characters, so we used about 50.
"
Anyway, just play around with that number until you get it right for your model.