I was a cabinetmaker in a past life. Curves can be tough, but I usually had more difficulty attaching the fabric to the curve after the substrate was formed, but it can be done. The most simple way to get and maintain the curve is to bend some 1/4" ply to the curve you want, and use yellow wood glue over the entire surface and attach another piece of 1/4" ply to the curved piece and dry for 24 hours. Then attach the fabric starting from the middle to each end.
--2005 F350 Superduty Crewcab, 6.0, 4wd, short bed, 3.73 gears;
--2016 Montana 3711FL, 40'
--2014 Wildcat 327CK, 38' SOLD