Remember how an oil can when pressed will pop back. Body panels where the metal is stretched will demonstrate the same pop back that an oil can does, aka oil canning. To fix this one needs to shrink the area so that the panel will lay flat. True body men will shrink the area with heat and cold, there is a shrinker disk I have read about never used. For me I put some cuts in the stretched area to remove some metal and then stitched it back and smoothed it. That may or may not be the proper way but it worked.