The only time CG effects directional stability is when it is too far aft and the plane is travelling slowly.
Whilst in high speed flight there will always be a bit of "Waggle" as the air acting on the vertical fin/s is not spread down the length of a fuselage and therefore only acts on parts of the craft aft of the nominal CG point. Such "waggle" is a feature of the beast and is normally not a serious issue UNLESS you have the CG too far aft and are travelling slowly where a stall and a wing drop can be expected.
Have fun!