Guys, figuring the safe range in which to locate the CG is affected by way more than just the MAC. In fact, the size of the horizontal tail and how far back it is could be the most important detail (pun intended). Even the wing's airfoil affects it.

The idea there is one best % of MAC to use ignores all but one detail. That there is one perfect percentage would be a great idea, but for it to be possible would only work if every airplane and model were all exactly the same and had the same wing and tail shapes, aspect ratios, tapers, airfoils, and a few others.

Over time the aviation world has narrowed down the formulas used to estimate CG locations and the simplest single computation happens to be available online. It happens to take 9 different measurements. http://adamone.rchomepage.com/cg_calc.htm It's actually quite simple to do as it only requires a yardstick or tape measure and 4 or 5 minutes.