Cut thru the shear webs and separate the sheeting from the ribs on bottom side where sheeting is near the trailing edge. Pin it all down then re-glue the sheeting (reach with scrap stick as glue applicator or get a syringe w long tip- use Titebond or similar) and install new shear webs. It may still have a little twist due to the sheeting at the leading edge. Good luck. P.S. it's a Hershey Bar wing and would be easy enough to just build another panel(?)