I deadlift conventional and have deadlifted in a inzer hardcore, titan centurian, metal deadlifter and metal viking deadlifter.
I found the inzer ok, but didn't get a lot from it- the titan had great pop off the floor, but I found it hard to get into position and I seemed to get jammed up in lockout with a rounded back (I think because my starting position was off). The metal suits are fantastic- both were great, but the viking was/is awesome. Seems to give support right through the lift.
I am right there with you...the most i got from my Inzer over raw was around20lbs. The most i got from my Titan was around 50lbs and that was after a fighting with it a few times to go down and grab the bar (i had to do it with no belt) one day i will try it with the belt and see how much i get.