I'd be interested in a "supported" solution to this as well. In the mean-time, I've kludged this together and it works for me...
Under "Page Menu Bar" options, "Font Size & Face," I replaced the default:
11px Arial, Verdana, sans-serif
6px Arial, Verdana, sans-serif; font-weight: bold; width: 9em; text-align: center
Which gives even-spacing (with the width attribute), and also centers each page title (with the text-align attribute) in each menu box.
ETA - Hi, Flynn! Looks like I was too slow on the draw and you already replied!