Stacking of Boxes/Volumes (Via Any Method, Kangaroo, etc.) - Need Help/Advice

Hello Grasshopper community,

I have a list of geometry boxes, randomly placed in a larger volume. The smaller volumes are predefined and the amount is randomly generated. The points where they are placed is also randomly generated. What I want now is that the boxes stack on each other and only move vertically while stacking. 

I already tried Packrat, but that's not what I'm looking for. Efficiency of stacking is not a focus in my project. I also tried to work with Kangaroo, but that didn't work out as I want. What I want to achieve is this: http://spacesymmetrystructure.wordpress.com/2012/12/30/orthogonal-c...

The Kangaroo is one of the solutions. However it does not make the boxes only move in vertical direction. Does someone know how I can achieve the same effect as in the link above?

Down below I'll include the file with the boxes and a file with the Kangaroo definition I tried to made.

What I hope is that the result is a composition made of stacked volumes that can be used in Architecture. The smaller volumes represent small houses. 

Summary:

I want to stack boxes on each other while only moving vertically.

Thank you in advance.

Greetings,

P.H. Danny Chan