Want to know where the CG should be for flight? Get a yardstick and make the 9 measurements this application ( http://www.geistware.com/rcmodeling/cg_super_calc.htm ) takes for input. Plug the measurements into the blanks and then fill in 5% for Static Margin and run the app. Record the CG returned. Then change the 5% to 15% and run the app again. The CG returned, combined with the 1st, is the reliably safe CG range for that airplane.