Well I am on a public computer at the moment and cannot look at the vid, so cannot comment on form. I do say, tho, that whatever it takes to get the damn thing up is fine. A heavy chain suspended GM will always look a lot like a squat, IMO.
I did this exercise last night as well, but did it at 39 inches and I made it up to mid 400's. Very tough exercise, and just a few inches in height difference makes a world of difference on the weight you are able to use. I have done these from 44ish inches and went over 600 lbs, and 400 was kicking my ass at 39 inches.
Stick with these. They are a great exercise I think. I would recommend varying height and stance on them, personally.
B.