CR4 & MoGraph Help (Building blocks falling into a shape)

I am trying to achieve the effect of cubes "falling" from 360 Degrees (only X and Y, no Z) to the center of a map of the USA until it "fills" the map. It want it to start with just a cube in the center and then more cubes stacking on each side of the original cube, "falling" at different rates, until the cubes form the the shape of the USA. Of course I just use MoGraph, but I am having problems from the start. I want the cubes to be in a matrix that is straight and aligned with each other and only one cube thick. Think of building blocks in the shape of the USA.

The only thing I have been able to do so far is have completely randomly placed cubes fill up a shape of the USA. With cubes intersecting each other, massive space between cubes, and cubes not even aligned in Z space and sticking out. Everything I done not want.

Any advice to achieve my intended effect would help. Thanks in advance.