I just bought a flex 920 used and I didn't get a manual. I just need info on how to calibrate the tension head and how to adjust the clamp base. I went to the website and is said look at the manual. I just need to know what I need to do to the head to calibrate the tension, ie what screws to turn and which way. The clamp bases are also slipping a little and I was wondering what to do about it.