As a general rule, it's more of an accident that the poop gets out, but, there are times when they will throw it out, to get your attention or tell you "Hey, it's time to clean my cage!" I change the cages weekly, but as it gets closer to the cleaning day, I notice more poop being on the floor. I keep a little broom/dustpan combo near the cage upstairs and a vacuum in each of the two chin rooms downstairs. You may not like to sweep or vacuum, but, it's allot better than stepping in it and taking it to other rooms on the bottom of your shoes or feet.
Remember: Poop is a waste ... it can carry bacteria and parasites that can be passed to others, some even to humans ... the cleaner, the better.
The cardboard shields are good, but will be chewed and have to be replaced. Plexi glass is good, just remember to keep it clean.
Jo Ann