Got sidelined due to storage space. Even had a kind of model.
Measurements of my planned one:
Quick and dirty model.
If you watch your video close, you can see everything below the top button on the vest is static. They probably notched the mirrors there to make it more comfortable, possibly some padding for the actor to lay in a bit, as you need to bend forward a tad to get the illusion to work best. The front panels further restrict viewing angle, which allows them to 'shorten' up the side walls a bit, OR place things in the foreground further and not have them reflect.
If you were to elevate the floor above the field of view, you can adjust the angles on the mirrors as well, as you no longer need a straight 'floor' reflection.