Your keeping 2 ousts in one cage? Thats not going to work for too long, the male will start stressing the female after a while in that small of a cage.
If you had a 4-5ft long cage you could just put a bunch of ficus in the middle as a visual barrier, and have 2 basking spots and feeding spots.
My only consern on the whole cage is the cham will be longer than the cage is wide. Even the female should hit 18".