Enrique,
Ensure that you have some washout in the wing panels to prevent tip stalls. If the wings are already built you can raiseboth ailerons about 3 mm to provide some washout. I am currently building one of the original BVMA-4s, about 1/8 scale, and the plans for for 1/8" or about 3 mm washout built into each wing panel.
I am also going to add vortex generators, outboard of the wing to help prevent tip stalling. These can be made from G-10 material and inserted into the wing skins before the final finish. The full scale A-4 had about a dozen vortex generators installed on the leading edge slat and about 2 dozen midway between the slat and the aileron. The slat set were aligned with the airflow and the wing set were aligned with the airflow inboard and gradually aligned toward the root as they went out to the wing tip. Good luck with yourSkyhawk.

Art ARRO