I brought my second racket to Sports Authority yesterday to get strung. The other one I got done at a local tennis pro shop that costs a few dollars more. I got the racket back today - it was supposed to be strung slightly tighter than the first, but right off the bat I noticed that it's a lot looser, probably at least 5lbs less tension than the first one. I went back there and found out that they calibrate their Babolat machine once a year, at the beginning of the year. Do you think that after 10 months of stringing, the calibration can be off by that much? The stringer is an older, experienced guy and I doubt he would mess it up that much, so it's probably the machine. I got a full refund for the string job and my strings.. so no big loss, except some wasted time.