How open are the cages? It might help to add some extra "stuff" to the cage fore security...something as simple as an extra PVC tube for hiding really made a difference for a friend of mine last season when he had a few picky eaters.
They are 6 qt sterlite tubs with just paper towels on the bottom. Maybe I should add some crushed newspaper to fill up some of the space. Maybe some aspen instead. Some of my smaller snakes seems to like and dig a little in it.