TabbedButtonBar : Justification request

For now the TabbedButtonBar buttons are always justified to the left (if horizontal) or to the top (if vertical).
It would be great to be able to change that, in order to get things like that for example:

I just added a quick stickToEnd() method to get that, but perhaps you guys can think of some neat idea to give it some flex options?

I think centered/stretch/right-justified tabs are quite a common need, what you think?