Years ago, while I was still wandering between Domination and submission, I managed to tear the nipple of a male bottom with my heel, thought I was trying to be very careful. It did scare the s... out of me.
The heels themselves were made of steel, but still...
I would definitely use some "second skin" latex.
Bet it wasn't a walk in the park for the guy either
Believe it or not he enjoyed it, he kept on pressing my heel at his nipple. His Mistress was pretty OK with it too, I guess they were a bit extreme, but wayyy to extreme for me.