Solved! Go to Solution.
If you go to the Option box for stack label (label manager>placement properties>fitting strategy) you have the option to force a split at a space (or a comma, an astrix, etc.) and if you're in 10.1 there is an option to constrain to center.
I don't remember the constrain to center option in 10.0, but the force split is definitely an option there.
Another thing to check is the minimum number of characters on a line. It defaults to 3 so that could be an issue for say, Substation #9