Down, there is something that might be rather easy to do to fix it! If you have a heating iron for iron on covering, you may be able to shrink the covering to correct any warping! Just find the area that is warped, and heat the opposite side, in this case top or bottom, to get the warping out. Now if the warp is more than heating the covering may fix, then you will have to resort to something a little more drastic. This fix, remove all of the covering from the tail area involved and slowly apply warm water to the warped area until it is soaked through. You want to make the area "bendable." then using 2 straight and flat surfaces and clamp them to the wet part making sure that you are seating them EXACTLY STRAIGHT, FLAT, AND INLINE with where the part needs to be. This envolves a lot of measuring before you start! Now leave the plane alone for 24 - 72 ... closer to 72... hours without being moved, nudged, or even thought about hard! This gives the part time to dry again and hopefully in the correct way to correct the warp. Hope this helps!

Reg