Just a question for you more experienced 3D fliers.

How critical is getting the right balance (COG)? Is this something worth tweaking?

getting it at the recommended is very critical.... after that and you are very comfortable with the plane you can move it in slight increments fore and/or aft until you find a position that you like best..

Lee is right on, get it to reccomended CG then you can play with it to get to your comfort level
a couple of things to remember--

1. nose heavy= fast landings

2. tail heavy= harder to control elevator,is real pitchy, hard to land.

good luck