I'm trying to do my thesis defense using sketches embedded within a giCentre slideshow.  The default arrangement works great, but I'm trying to customize it a little.

The specific problem I am having is to fill different regions of a single slide with unique sketches, all on a uniform background image that all take a single argument that controls the content of each sketch. How do I arrange them in a particular grid (see example)? How can I pass arguments to each sketch from the parent slide?