I have had three biplanes and I have no idea how I balance them (that is, I have no plan on how to do it). One is my own design so I had to decide on the CG location. I just balance it. Top wing, bottom wing, fuselage. If the CG is in mid-space, it will give you an opportunity to solve the problem and you will learn a lot from that. That point is always only a starting point. Slight CG adjustment is usually needed for optimum performance.