68 Deluxe Buckets

Has anyone restored a set of Deluxe Buckets out of a 68 fish? They have a cardboard panel at the back of the seat back, and the used buckets I bought were missing these and I have no idea how to attach the new panels. Do these new cardboard pieces need to be trimmed first, they look like they are too big, they come with four square holes in them so I presume I need some sort of clip.