I did this exact same thing for the rotting visors on my wife'* previous `88 Grand Prix when I redid the headliner. But after I cut the pieces of material and sewed them together, I had a shoe repair shop stitch all around them, because they have sewing machines made for stitching soles onto shoes, and they were perfect for stitching around the visor. They looked really nice. I sold the car to a friend who still has it, so if he ever stops by, I'll take pictures.
I absolutely HATE the airbag warning stickers and would very much like to recover my visors, but with nothing else wrong with them, I am very reluctant to tear them all apart, so for now I just live with it. I hate idiot warnings in general, and I was horrified when they apparently became mandatory on US cars.
97 SE, teflon wiper blades, Dunlop Sport A-2 tires, Leather steering wheel cover, Pioneer DEH-P480MP mp3 CDRW head unit, Pioneer 12-disc changer, iPod hookup, Boston Acoustic 3 way 6x9'*, Boston acoustic separates in door pods, Alpine 4 channel amp in trunk. Magnaflow dual outlet muffler and Ractive stainless tips. Autozone rice pipe and K&N 4750 intake kit. Clear corner lights. Energy Suspension end links.