After I built my EF-16, I found the left wing to be slightly warped. I mean you could barely see it. I heated up the discerepant wing with a monokote heat gun, twisted the wing in the correct position and, held it there untill the wing cooled down. Now both of my 16s fly with zero trim. I found the balance to be the best at the most forward part of the opening of the cheater hole. I covered my 16s with sign vinyl. Vinyl works the best when covering foam models with compound curves. Just add a little heat to make it conform to any shape. good luck.