hi melissa,
so the way the templates are set up, there was no real easy way to modify the fundamental domain at whim... i have made a rhombus p1 for personal use, but it's not clean enough for me to post it on the site. it's currently on another computer which is getting repaired, when i get it back i could send you it.
as for building them on your own, it shouldn't be too hard. if you look through all the layers in a template, you should be able to find one with about 4 transform effects applied to it. this is where most of the magic happens. the key trick that i do to make working with the transform function a bit nicer is to add "dummy shapes" that are empty squares that are way larger than any of the artwork i will be drawing. the reason this is necessary is because the transform effect draws a bounding box around the layer and then applies its effects from there. if you don't have a large dummy bounding box, then as you draw, the bounding box will change and the transform effect will change.
i know it's a bit unclear, illustrator is ridiculous... but i hope this helps!
-matt