I use a 2x3’ dog crate subdivided too and bottom and it works fine for 4 weeks and older birds (chicks can squeeze through the bars). My quail can stick their heads out but it is wide enough they don’t get stuck either. Can you subdivide into 3 cages, that would fix your height issue. Also, I’m not sure enclosing 5/6 sides is a good idea (light, ventilation, sanitation would all suffer). I put a 3-4 inch rim around the base of each level to ‘hold’ shavings in and give a ledge for water bottle bases/tips. Birds need a square foot of floor space (minus feeders, etc) each. Mine live in the garage and so far no issues with predators though there are plenty around, especially cats. Quail keeping is an art not a science, do what works for you and your birds (within the basic parameters of course like cage height) and you’ll always be learning and tinkering and changing things as you go, it’s a journey not a sprint.