The PAPIs are calibrated to give 2 white 2 red if you are at 50' over the threshold. The ILS is calibrated exactly the same, so that you touch down within the touchdown zone markers. Obviously not designed for light aircraft....unless you want to land in the touchdown zone markers of course!
As for the rate of descent, well its definitely not 0 fpm, and not 750 fpm
Our GPWS callouts are at 10' intervals from 50'-10' and they deafen you at around 1 per 1.5 seconds, and then a slight flare probably reduces it to between 200-100 fpm. I'll have a look next time.
tomcs