If you used white glue on the sheeting or some other water-based glue, you can spray everything down with windex and pin it back to the board and let her dry. Some of the twist will come out when you attach the top to the bottom. If she still is twisted to much, you can repeat, but this time place shimes under the fuselage so that you can "over" torque when you pin down. These things can sometimes be hard to fix without re-sheeting.