Yes, it can easily taper that much. I've run into a fair amount of brass that tapers in the neck area, it readily shows itself when neck turning it.
I think mathman sets them up the same way I do. My rockchucker cams over right at the end of the stroke when I have them set up the way I like. I set them by feel, I've learned what the proper force feels like so it'll cam over without blowing the top off the die.
