SPHERE PACKING - SPHERE COLLISION?

Hi,

I'm trying something similar within this thread : http://www.grasshopper3d.com/forum/topics/balloon-packing-voronoi

It doesn't seem like it got very far in that discussion, but now that Kangaroo is a bit more advanced, I assume it can do this more easily? I've managed to MESH SPRING a sphere within a box to at least collide with it and apply a unary Z force to each vertice. However, I can do this with one sphere, but I still haven't figured out a clear way to collide among multiple spheres and also apply a decent pressure force so that it bulges out as it collides against the box. As of right now, it's very basic and does not react how a regular water balloon would in real life.