Lots of good suggestions have been given.

To improve the basic Stik use wide packing tape and cover the inner gap between the wings.

To improve the strength of the wings and stop the large amount of bending in loops, etc. use a basic guying system.

Go out on each wing about halfway out from the fuselage and 25% aft of the leading edge of the wing. Glue on some 1 inch diameter reinforcement circles on the top of the wing.

Run thich string from one wing down to about 1/2 of the way down on the gear leg on that side.

Tie a knot and put some glue to hold it in place to stop slipping on the gear leg. Run the string across to the other landing gear leg, knot it, and then up to the wing on the other side.

When the airloads are applied to the wing they try to pull the landing gear up which can't because the string keeps them in place.

You can pull any king of up load maneuvers and the wings won't bend.

By the way the airplane control response to roll is much better if you add polyhedral to about the outer 40% (the numbers are only approximates, not critical) of the wing panels. Make it about 1 inch up from the bottom of the wing.

I have had mine now since they first came out. A nice airplane and works in the street in the front of the house. New subdivision and no trees yet.

I hope there is a picture below.