As always, Raj nails it. One note though. Regardless of weather the tank is on the CG or in the stock location it does not change the required CG for the plane, weather you choose the advised CG of 4 7/8" or a more agressive aft CG as RAJ pointed out. CG is in direct relation to the mean aerodynamic chord of the wing(MAC) and its placement at the center of mass of the fuse (COM). Regardless where you choose to distribute the location of the components. Joe