for the fronts i believe... not sure about the rears.
i went all the way down on my d2's this weekend, granted i havent removed the perches, and its not THAT low :S i wanted to tuck rim lol
yea, my fronts have like 1.5" of threads left, and the rears are all the way down. once i do my brakes im gonna go lower by taking out one or two of the rings in the rear, and just lower the front just as much.