You can rig up a bolt mounting. The cross members, 1/4" ply will need to be added, one under the TE of the wing, and one under the LE.Use some tri stock, 3/8" minimum to give a better grip to the ply.

It is going to require some opening up of the wing, get under the top sheeting so you can add some balsa, preferably end grain, for the screws to tighten on. Sand the fillers flush with the top sheeting and cap with some 1/16" ply.

Rubber band the wing down tight and drill one hole through the wing and new 1/4" ply with a #7 drill. Remove the wing and redrill the hole in the wing with a 1/4" drill. Mount the wing back on the fuselage with rubber bands, and then tap the ply using the hole in the wing as a guide. put in a nylon bolt and then repeat the drill, tap sequence on a hole on the other edge of the wing. Now with two screws in place, drill the other two holes, and tap them. Now, take the wing off and run a generous amount of THIN CA in the tapped holes. Hit is with some accerator and then re-tap them, being careful to not cross thread. This hardens the threads up for long life. Bolt on the wing and go fly. Opps, cover the ply with some covering, then go fly.

Don