Not sure about a coupe but i have some new window crank covers(i'm assuming this is the part you speak of because it is the only area back there with any board) i bought for my convertible about 10+ years ago i never installed yet and the boards are glued to the vinyl and underlayment with the exception of the area where the trim piece is installed and the area above the board, the vinyl and padding is no glued.These will be glued to your old metal piece that you need to reuse with your windowfelt and then glue all together as one.They should be a bit solid but will have a bit of flimsyness to them because they are technically split between the metal and board but will be solid once installed on the body.Here are a few shots of mine:



Hope this is of some help

David