Is this really a concern. My girl is almost three ft long and the tallest point on the branch is maybe 7-8 inches. I cannot see her causing any real damage falling from that height. Forgive me for being blunt, but isn't this Darwin at work. Heck I have fallen from a few roofs in my day and I am still kickin. ;-)
In all reality though, not sure that I am realy afraid of an injury from her falling. She actually moves around on the branch quite well. Maybe she just has a lot of practice at it as like I have said, she has had the same cage for quite a while now.