[cctalk] QIC tape replacement bands

Hi all, I am looking for advice on some problems that I am observing trying to read QIC tapes using an Archive Viper. If you are unfamiliar with QIC tapes, tape transport is done through a single roller that moves a plastic band in tension with the outside of a  portion of the tape on the reels. Over time, the band will break. A long time ago, I bought a bunch of the green plastibands to use as replacement bands. Later I bought a bunch of the clear ones. I was able to image some tapes with the plastiband replacement but not all (but rewind and retension works almost every time). Until today, I don't think I ever tried the clear ones after I bought a bag. I am preparing for a VCF and need the contents off of some of the tapes that I have, so I got out the driver and tapes. However, I have been unable to read anything from the them. The tape will jam up. It seems like what is happening is that plastiband is not providing enough tension to move the tape when reading. The tape loses tension and I see it gather instead of moving along. Sometimes the tape feels stuck to the posts that turn the tape to be parallel with the heads. I also tried a clear band for the first time and the tension with that seems too tight. What am I doing wrong? alan