That method of considering the wings as one can work if both wings are the same and there's no sweep, but with this plane it could make him really nose heavy. It only takes about 5 minutes to take the measurements and plug them into the calculator above. That will give him the correct CG for each wing, and then he locates it in between the two on the plane. That will be the technically correct CG, which he can then adjust to suit his tastes afterward.