Android : Aligning ImageViews in the form of wall-clock numbers

I'm writing a clock application, in which every number is a unique drawable that can change during the run of the activity (meaning, there is a great group of drawable possibilities for each number).

I want to define the layout so that the ImageViews will be aligned in the form of a clock:

My problem is, that since every number is an ImageView of its own, then I can't properly align numbers such as '1','2','4','5','7' etc. The edge numbers could be easily aligned to the parent top+center etc.

I've seen similar questions asking for circular aligning of images, but in all they assumed the center is known, and I want to make this screen-size independent.

Thanks for any suggestion!