I've been using the Powerdisc attached to a 371 gram 2pts HL prestige classic for a total weight of 15 oz for the last week and my hand speed on all the strokes is noticeably higher than before training when I remove the weight. I feel the extra heft forces me to use my legs more and less of the smaller muscles. (A very good thing). More racket head speed probably do to less "lazy cheating" with smaller muscles. Only problem is that it feels so good and solid when I hit with it on, that I don't want to take it off. I know someone posted about this thing before. Anyone else have any experiences with it?