I don't know who told you to balance the wings... but they are very smart.

Balancing the AC laterally is just as important as placing the CG, it will make the AC much easier to fly and trim.

I prefer to balance the AC before the covering is on - that way any weight that is added can be 'Hidden' under the covering. It also makes for a much nicer looking plane...

Make sure all components are in place (Engine, rudder, ailerons MUFFLER etc).

Then hang the AC from the ceiling by a fine rope around the prop shaft and one to the tail. Centre the rope and let gravity go to work... []

Balance the plane by adding small weights to the light wing tip (Start with pennies) Once the balance has been worked out secure the weight to the wing and cover / recover the wing