I bought one used prostaff 85 from a local tennis shop. This one is playing stiffer that the one I bought from TW. It says prostaff instead of prostaff 6.0 on the beam. The handle was customized and I can't tell where it was made. I measured the beam width using a digital caliber, it is 17.8 mm, the one from TW is 17.1 mm. Which version ps 6.0 I got? Thx!