Does anyone have a good method to determine the amount of contact between the hammer and the nipples (if any)?
I don't know if this will work for this application as I've never actually tried it, but in theory at least it ought to. I have used it in other places for similar purposes with a lot of sucess.
Try several layers of trimmed electrical tape, adding & removing layers as needed till you get an imprint of the nipple's face as the hammer drops on the tape (which will also protect the nipple end?????).
Once you've got the impring right just measure the tape patches with a mic & you're GTG.