Ok, somebody is confused here and maybe its me, but here's how I see it. Ever other window is clipped. The raised portion in center of clip does not support any weight. It's there as a guide, between the two rails, to keep the track from coming off.
There's a rail on each side of the "raised" center part of the "clip"! Where do you guys get that only the left side is clipped? That clip supports both rails, they run that close together!
There's one "mono" rail with two hifax underneath. Both ride on those clips. One on each side of the raised center. Please explain to me how only the left side is going to wear out?
Either I'm confused on what your trying to say or some of you guys haven't seen one in real life.
I think their saying with it clipped every other window the clips will always be on the same side that the track lugs are because the lugs are staggered too