i'll let you know how it goes with the hack squat. i've done the deadlift in the past... i know that it works the upper body to a great extent. i would never assemble a routine that didn't involve some type of deadlift! i figure i'm getting all of the upper body benefits of the deadlift from the stiff/straight-legged deadlift (not to mention the same/a greater degree of lower back stimulation.) the reason that i'm using the hack squat is due to the fact that i really want to try to bring up my legs, which aren't as strong as i'd like. i don't know if i'm the only one here, but my deadlift has never been that great. i once topped off at 355 in the stiff-legged deadlift, though... and, at a height of 5'4", and a bodyweight of roughly 130 at the time, i don't think that's too shabby. i'm a little guy, what can i say? since i've started lifting with hst principles, though, a little over a year ago, i've gained about 10 lbs. of lean body mass. i hope these results continue. knock on wood.