Having built (a boat) to my own design in stitch and glue, I can confirm that it is not easy to get wide nearly-flat panels to bend well - you are inclined to get the stitched edges forming the desired curve while the centre of the panel flattens out considerably in between supports. Framing is still required on large nearly-flat panels.
There is a reason why stitch and glue boats are often made from long narrow panels which all curve continuously!
Andrew