Tried searching, no luck

Have a 91 300D that I removed the rear window stainless trim on for repainting. . . The stainless trim has a rubber seal, and the backglass, when I removed the stainless, had a u-channel piece of rubber which was on the side and top of the glass. This u-channel rubber has ridges on one side. I have tried putting the u-channel rubber on the glass (ridges up), and then reinstalling the trim, but the rubber moves. Also tried putting the rubber in the channel in the trim, but that didn't work. Should I glue it to the glass? to the stainless trim?

This is very frustrating All suggestions appreciated)