I learned the hard way that there is no easy way to
"Pin Down" CG exactly the first time, but this should get it close enough
to fly and then adjust as necessary.
Static Margin should be between 5% and 15% for a good stability. A 15%
Static Margin is generally accepted as a good
starting point for the CG of a conventional tailed aircraft. Too much Static Margin makes the aircraft nose-heavy.