Gregory, I did the same thing with this plane. I'm using a DLE 20. Robart air retracts. 6.0v battery mounted just behind the wing saddle. I built a compartment just in front of the tail wheel for a 4.8v battery. Balanced without adding any weight. CG is 5.25 inches back from the leading edge of the wing at the fuselage. Total weight is 11 lbs. Flies good at this weight. I have over 300 flights in eight years. I reinforced the gear mounts during assembly as they were a weak point.