U Can Do 3D
Jim,
My UCD balances at about 5 1/4 to 5 1/2 inches from the leading edge. The tank is positioned over the CG. My 6v 1700 mAh NiCd pack is right behind the second former (right behind the tank) The throttle servo and receiver are right behind this at the rear of the wing compartment. No lead has been added. Another identical setup has 3-4 oz under the tail to make it balance around 6 inches back.
Chris
(I'm sure you've all seen one by now but I just had to post a picture)