For lateral balancing I use a loop of safety wire inserted under the upper most hinge on the rudder and a string that is run from the prop hub thru the safety wire loop. I tie a loop in the string somewhere near the CG point just so that the plane hangs evenly (neither nose up nor nose down). Most of the plane's mass is below the line between the hinge and the prop hub  so it will easily hang even if a wing is out of balance by an ounce. This has worked on low wing, mid wing, high wing and bi-planes.