I am looking at getting a new track or buying one from a buddy. I have a 2000 Polaris 600 XCSP and he has a 2000 Ski-Doo MXZ 600. Are their tracks compatable? What does it mean on the track for windows, all open and 2 open, 1 closed? Isn't that where the drive wheel drives the track? How can there be closed windows? I don't have my sled here so I can look at the existing but it seems weird that you can have closed windows. I see it on the more aggressive tracks 1.25" plus.