I just put a piece (about 1" by 1" by 1/4") of foam rubber insulation between the two plexiglass panels at the top of side curtain. One side had a plastic (?) cover over what I suppose was some sticky glue. I left the plastic in place and it slides when I open the window, while the side, with no plastic, stays in place. If it falls out, I just make another!! Stops the rattle for me!
