This is an excellent question that I too would like the answer to. Since you posted this question quite some time ago, perhaps you have the answer. All I've been doing is winging it, by editing layout and manually centering, trying in the process to be conssitent. I have found no source of infromation that addresses this issue. It seems that the software should be such that it is automatically center. Why not?
Again, good question. Hope there is a fix to your irritation, and mine.