When comparing the wing to that of an Ultra Stick Lite (somewhat smaller), the USL uses aft spars (four spars). Perhaps the USL was overbuilt or they used four spars to deal with crow where larger ailerons and flaps are presenting mid wing panel forces that would tend to twist the panel and cause wash in. It doesn't appear that you are setting your stick up for crow, so my comment is really addressed to those who might build this model with a crow setup... should the wing have aft spars if using a crow setup?