Post paint elevators and ailerons have to be checked for balance. The purpose is to prove these flight controls resistant to flutter. This is done by showing that the given control surface was built to have a center of gravity forward of the hinge point.
The elevator is easy to test - set up a knife edge, suspend the part from its hinge pin, and compare the part to a level. The photos below are sequenced to show the set up and then the result for both right and left elevators. The elevators passed, the left easily, the right by a narrow margin, both without requiring additional weights and / sanding. For the Cozy, this counts as a pass with no problems.
The aileron is harder to test - it is heavy and clumsy and there is no pin long enough to allow use of the same knife edge test. For the aileron, the test is to suspend the part from the center of the hinge and then compare the part to a level. The photos show the set up and then the result for both right and left ailerons. The ailerons passed with a narrow margin - I documented it with the level to make sure I was seeing it correctly.