Hey Motor,

It is very easy to put a warp in a wing by simply shinking the covering too much. You could put the wing on a flat surface and careful force the wing to sit flat WHILE heating the covering back up. You will have to do the same thing on the underside of the wing once you have done the top. What I do here is use a heat gun and try to maintain some heat all along the wing panel and once you have reached the point where you can stretch or shrink it, lay the bottom of the wing panel back on the flat surface and hold it there for a minute or so.

While holding the wing down when you finished step two, reheat the top and continue to hold it there. If the warp was caused by the covering shrinkage, this should fix your problem.