I'd say 1/2", its actually sticking out the bottom of the hole just slightly, maybe 1/8"
Tomorrow I'm going to see if I can get ahold of the bottom end with some small vice grips or something and see if I can turn it, if so I could screw it on through and out the bottom.
Tried the punch ground to a point to try and get it to turn, but its down in the hole enough that I can only hit it in one place, cant go back and forth across the flutes.