I put a travelling type of cage inside a bigger crate and I have found that works well. Even at 6 months she has plenty of room for sleeping but if she was desperate she could find a place inside the big crate though there isnt really room to walk around. I find she stays in the sleeping cage until I let her out in the morning and has never messed in it. I have a feeling that if she had been just in the bigger cage she would have had enough room to be tempted to mess at night.