Project is once again done, but not before I had another measurement scare. As I was working on the front door hinges, I realized the doors wouldn't close! The glass was hitting the frontmost piece of the printer (two timing belt pulleys on the top front corners). My measurement of the 3D printer was not accurate enough. I was very lucky -- the error was very small. The depth of the cage only needed to be about 10 mm deeper. I was able to pick up this extra depth by changing the framework of the rear face from 2020 extrusion to 2040. This gave me an extra 20 mm depth, more than enough, the the only down side is that the top lid is a little short, but even that I could fix if it worries me too much down the road.
If you have an Ender 5 and want to build this kind of cage, I would increase the depth by more than 20 mm, just to give a little more margin. I would probably bump the depth say 50 mm?