Could I use some cut out cardboard circles for my speakers I found? It's pretty thick and wanted to use it to be a spacer between the front of the speaker to door panel so like a funnel to the panel not to be mistaken from the back of the speaker to the panel bit the front of the cone to transfer waves and thinking of using balistic mat to cover the cardboard and maybe sticky it on the cone of the speaker or maybe glue? Or is this a horrible idea?