When you finally fly it, you can check to see if the calculations were correct by flying it inverted.
If you have to push lots of forward stick then it's nose heavy.
A little forward stick is a correct.
If it doesn't climb or dive and still flies well then that's it's acceptable but marginal.
If it climbs when inverted then it's tail heavy and will possibly have stability issues.
The model will have less drag if the cg is correct and will generally fly faster as the elevator drag will be reduced. Not sure you would notice on a model but airliners can save substantial amounts of fuel by moving the cg back as far as they can.
Jim