I took the liberty of making up a couple of example pics in photoshop of more realistic cage designs. These are by no means comprehensive designs, just showing where extra reinforcement might go, you're best to research it yourself.
There are many variations, like replacing the taxi bar with a diagonal, different combinations of diagonals in the rear etc.
I also added a front half to the cage in one pic, including cross bars and diagonal roof bar.
Half cage with simple reinforcements:
Full cage...
