CG can make the difference between a good flying plane and a great flying plane. It is also a matter of how you plan to fly the plane. A 3D aerobat may need a different center than a 3 channel trainer.

For example my Aerobird, a RTF, comes perfectly balanced for a 6 cell battery. The company makes a 7 cell option available but makes no provision to move the battery back to maintain the CG.

The plane flies fine under power, but if you are gliding or just crusing at half throttle, it wants to nose down so you always have some back adjustment on the elevator. You have to work a little harder to make the plane fly smoothly.

Also, when you hand launch this electric, it drops more than you would like with the 7 cell even though the 7 cell has more power.

So, I cut the foam that sets the location of the 6 cell to move the 7 cell back 1/2 inch. Now she launches better glides better and cruises at half throttle much better.

That is what a minor move in CG does.

Hope that helps.