CG is important especially for the maiden fligh. as mentioned "at min it should be in the acceptable zone". but dead on is best.Even a cm out can give a lot of grief in a maiden flight if even 1 surface is out of trim which is enoughg to handle.
Nose heavy a plane flies poorly tail heavy it flies once then bang
a pivot balancer and even fingertips works ok .
I have had the same issue with a low wing plane giving a tail heavy result when the CG was correct with the plane rightway up
So I suggest all low wingers be balanced Upsidedown. The hobbyking CG blancer is a beaut as are any of the other types.