Aerodynamic excitation may be less forgiving than static tests. I used to use a forklift and scale and rules to evaluate racing sailboat parts but under real racing some failed after that. A finish that is less elastic than the wing might also help give you a stress map. I would LISTEN INTENTLY...
I would go with fiberglass sandwich. Wood rot may come back at you later and you need to know enough about wiring to prevent galvinic corrosion in the aluminum.
