2 suggestions:
1) A very simple way of increasing the wing's angle of attack is to put a popsicle stick under the leading edge of the wing and fuse. If it doesn't takeoff, then add another stick and redo. Explore what angle of attack is best for you and then add that shim to the fuse leading edge.
2) Suggest you use more than one set of rubber bands to hold wing on. If one breaks, the wing will most likely cause major damage to your bird. Or the wing can start flopping in the air when yanking the plane around.