the problem with cloth panels is, that each piece is must be planar to create the panel. that means, each panel must be non folded 2d geometry. the easiest to do is using a orthogonal view (front, side, top) and build the curves there, only using this plane. if that worked out, you group the curves together and rotate them to be there they roughly should be. but they stay in this plane. (edit: important to note, they are not supposed to stay in the plane you modeled them, but they stay flat like a piece of paper, if you know what i mean) if you stitch 2 cloth panels together, they need not be in one plane though. that means 2 panels on top of each other with a bit distance create a u-turn thingy if you stitch togeter one side of the panels.

hope that helps