I forgot to point out that the reason for balancing is to help prevent flutter.
I'm no aeronautical genius, but my understanding is that when a surface starts fluttering it gets worse and worse due to the weight of the surface. IE: it starts moving and the weight of itself tries to keep it moving in that direction.
With it balanced, the weight is the same (or close) on each side of the hinge, which cancels the momentum of the surface.

I think the balances on the Ultra Sport are just for looks, and doesn't really make any difference.
However, I haven't looked at them or weighed them to see how much they are balanced.
If a surface is 100% balanced you can disconnect the linkage and the surface should "float" in a neutral position. You can't really check it like this unless you have it freely hinged.
Any % of balance helps and 100% is not necessary.
I know for a fact that on a full scale Cessna 172 the elevator isn't 100% balanced.

There are many different opinions on all this, and I'm sure that a search on this would bring up plenty of material.

Bill