It all depends on your support. If the base is stable, it's easier to create a higher structure. I don't recommend you going more than 5 squares high unless your first level have ample support at the bottom. I actually recommend you to build wider instead of higher because there's less chance of the whole thing collapsing. I have a wood base which the first level is zipped-tied but I cross-crossed it for better support. (just drill holes in a piece of wood and work the zip ties through) I put chloroplast to make cleaner suffice. But I also use thin wooden planks to support my shelves as well as stabilize the levels when I built it higher. Hope this helps.
