I'm late to this answer and I suspect you've had several excellent answers already, but I wanted to say two things - one, you can actually buy a lid made for a puppy pen - I have one I use over ex-pens when I need temporary holding for birds, and it doubles as a barrier from time to time as well; and, as far as leghorns, they can be an adjustment, but they are so worth the adjustment. They are easy keepers, produce more eggs per pound of feed than any other breed, and as long as they have enough space, in my experience they have not been inclined to pick at other birds. Those big, beautiful white eggs will be so rewarding