The main "secret" is detailed in the manual: you must have both wing halves fit together with absolutely no gaps, and have it glued well. We've seen a number of wings that have folded in flight, and almost all of them were very-poorly glued together. You must get the spars glued together, the leading and trailing edges glued together, and the center ribs and sheeting. All of the pieces contribute to the wing's strength. Also use at least a 30-minute epoxy. Epoxies with longer cure times are good, too.

When you assemble the wings, you must trial-fit them so that there's no gap in the center section, and the apply enough glue so that it will ooze out of the spar pockets and from between the two wing halves. Wipe off the squeeze, and clean up the area with rubbing alcohol on a rag. You'll be find once the glue cures.