MM- Original thought was a 1 x 4 poplar frame, leaving a 1" "border" around the screen to attach black velvet trim. With 1 x 4 being 3/4 x 3 1/2 actual size, leaving the 1" will give me 2 1/2 of attachment area around the perimeter of the Sintra. Is that enough to keep the Sintra flat, or will it bow in the center? I assume if it does bow, it will bow inward, so I could put in a vertical center support. If I do need the center support, should I glue the Sintra to it or let it float over the support?