My beardies had a 4x2x2, but I sold them quite a few years ago now, I just like the pic!
I'm not too worried about the crack, looking at your topic yours looked quite a big one(?). But my crack doesn't even touch the surface of the glass so all the silicon between the sheets around the hole should hold it tight, plus it will be under the bulkheads gasket.
Thanks for your concern though.