Anything you add, or leave off for that matter, not only affects the C.G. (balance point) but the wing loading as well. The plans should show a "C.G. range" as an elipse split into four quadrants. If the plane balances in this range you should not have a problem, unless the incidence is off at the wing, stab, or both. If it is clearly ahead of or behind the "suggested C.G. range" then it should be adjusted accordingly. As for the CG Machine, if used properly, it is a good tool.