Dynamically balancing the wings
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This method is very similar to balancing heli blades.
In fact, most of the times pilots only check the CG, which is the balance in one axis only.
You should also check the balance in the other axis, which means : do both wings have the same weight ?
In 99% of the cases, builders don't check it, they simply correct it in the maiden flight with aileron trim and ignore the fact that the plane is, albeit flying straight after trim, not making nice loopings anymore or not rolling axial.
This has to do with balancing (as one of the reasons, next to unequal throws etc).
Not only the wings should have the same weight (= statical balancing), they should also have the CG on the same spot, while having the same weight as well.
I found that on my L-39, there was a difference between both wings of 23 grams (half the weight of a good servo). I found this by putting them on a very accurate digital balance. Where I had to add the lead of 23 grams, was determined by the method identical to dynamically balancing rotor blades. If not, the balance would have been statical but most likely not dynamical. Especially in high G-maneuvers, this should still result in necessary corrective stick movement on ailerons, rudder or elevator, for example to keep the loops in the right vertical plane.
Watch the very informative video below, and you will understand the method. Do not forget to create a user in Helifreak.com first, or you will not have access to the videos.

http://video.helifreak.com/?subpath=...lancing101.wmv

Nicolas.