Unfortunately, the issue of pitch stability really isn't that simple. And the wing's center of pressure is much like "the man behind the curtain" in Alice in Wonderland for the average modeler of today. It really isn't true the CG should always be on a wing's maximum thickness.

Finding a starting point of a CG for a model today should actually take into consideration the things that affect pitch stability, like the model's tail, the part of the model that controls pitch. And it's best if figuring that is simple. All that's needed in fact is a yardstick or tape measure. The link below actually is that simple to use. All the modeler needs to know is where the tip, root, span, and sweep are and be able to measure them. By plugging in 5 and then 15 to the green box gives the suggested range for where to locate your start CG.

And it takes into consideration what your model has to control the pitch, the size and location of the horizontal tail.




http://adamone.rchomepage.com/cg_calc.htm