Be sure to make sure your plane is trimmed correctly and that the two elevator halves are parallel. If the elevator halves are not even, the plane can roll slightly when you apply it.

When I do a lateral balance, I attach a string from the engine drive hub to the tail wheel. I then suspend this from a hook in my garage ceiling. I may loop the string around the hook a few times so the plane doesn't slide for and aft. You'll immediately see if one side is heavy. I tape weights on the high wing tip until it is balanced. You can remove some wing covering and permanently epoxy the weights inside or just screw them on the wing tip if it isn't too much. Another option is to sink screws or nails into the wing tip for weight. It is also a good idea to recheck the CG after the lateral balance unless you put your weights right in line with CG.