Once covered, the wing is quite strong.

If you have not attached the ailerons yet, may I make a modification suggestion?

Add an extra hinge 1 bay in from the wingtip. The 4* 40 has a big wing and really floats. After flying a season or two, you can make the plane a little more aerobatic by cutting a bay off each wing, shortening the wingspan by about 6 inches. The plane will roll quicker but still be a gentle lander. If you add an extra hinge during construction, it will be there to support the ailerons at the new wingtip location. If you don't clip the wings, it'll only make the attachment of the ailerons stronger.

Scott