I've used a food dehydrator to straighten warped bodies. I make a jig that allows the body to end up in the proper position, clamp the body in the jig, and "cook" overnight in the dehydrator. Tray to place the clamps where they will not cause another warp, however, and allow the whole assembly to cool off naturally (no refrigerators, cold water, etc.).
Your promo might require several iterations of the above approach.