Side trim strips: they were all stuffed brimful of stiff window putty. Keeps things cleaner after weather, and protects the clips from their own rust. Position each clip, spot-putty in place, then position the next one. One at a time. Then fill in the gaps before popping them in. I have no idea how they got stuffed exactly right at the factory, but heating them before popping-in might work to get excess putty to squeeze out, and in precise final positioning.. [dead-blow hammer might help with that].