If your mfg only gave you ONE CG location, it's time to learn some more about aerodynamics. And it's time to place that mfg into the "makes Barbie dolls when not making ARFs" category.

If you get locked into the belief that only one CG matters and that you've got to get the plane balanced on it for the plane to fly safely, you're at the mercy of any toy manufacturing ARF mfg you're unlucky enough to encounter. And your next model will probably come from one.

Aircraft pitch stability isn't easy to understand, but it's not beyond most people. It's basically a function of how big the wing is, how long the wing chord is, and how big the horizontal tail is and how far back that is. There are a number of other modifiers but they aren't major players. Take a look at the measurements needed to figure a CG location and you'll see a bunch of formulas. They boil down to finding the above 4 things. Look at http://www.geistware.com/rcmodeling/cg_super_calc.htm and you'll see all that stuff.

It unfortunately scares lots of people off.

All that stuff basically figures out how big the tail is and how far back. And how big the wing is and it's chord and "where it is on the airplane". And all you have to do to get that all figured out for you is to provide 9 measurements you can do with a yardstick.