I like it to balance. Back when I used the same reel as I did for my graphite sticks, I had a spool for the boo rod with lead wraps below the backing. Then I got a heavier, large arbor for the boo so I don't do that anymore.
Of course, balance is a function of not only the weight, but the length and taper. Boo's heavier, yeah, but in many cases also shorter so it balances with a similar amount of weight. A long boo rod, though, needs the weight.
And the same is true for graphite rods. I want them balanced, and they do vary some, just not as much.
My rule of thumb is that I want the balance point of the rod and reel combo to be right around where the front of the cork meets the bottom of the blank. +/- an inch is fine. My casting style is to overpower everything, so many with a more traditional cast want it even farther back than that, closer to where your hand grips the cork. You can test it just by balancing the rod on your finger and figuring out where it balances. That's with the line strung and line hanging from the rod tip to the ground, as the line does make a significant difference (removes weight from the reel and adds it to the very end, basically).
Agree it's not so much about how well it casts. Maybe a little. But it's more about how much effort it takes to cast. The balance point is the center of gravity of the rod. The farther your hand from that center of gravity, the more momentum you are fighting with every acceleration and deceleration during the cast.
