since DH is a DC guy it's interesting to note that what Dante refers to as drag curls are not the "classical" version of the movement. DC has his guys do a regular BB curl for the first part of the movement then for the negative you lower the weight as you would a regular drag curl, that might be why Dave Henry's form looks all f'd up....I haven't seen the clip for along time so I don't remember.
I do regular drag curls and they're great.