I just saw this thread. Congrats on the new puppy! As for whether a plastic or metal pen is better, the only one we have used was the metal. It was so light weight that our puppy just pushed it wherever he wanted to go. If I needed a pen again I think I would go with the plastic one. As for something to put down I would go with some small inexpensive throw rugs that you can put in a washing machine.
Pam, Mom to
Thor-male brindle 05/24/01
Arabella-female brindle 12/19/06
Star-at the bridge 05/13/98-11/22/08