I just ordered a new x-pen for Sophie on Saturday (shes getting too big for her cage lol), it will be here soon and I need to figure out what to use as the floor! I was thinking about those foam puzzle pads (but she likes to chew), or a coroplast bottom to go around the outside with carpet on the inside. I was wondering if anyone could give me an idea of what to do!  Its an 8 panel so Im going to make it a square 4x4 so it fits in my room.

I have bed sheets (2 sets, I change it every Friday and throw it in the wash). It's mostly to protect my carpet from the carpet-crazy Cinnabun. She really likes it. I wanted to get something like you were considering with the puzzle pads, but in the end I went with sheets cause they were a bit cheaper and softer. Here's a pic of her in her in Xpen before bed time. It's also a 4x4 but I made it rectangular to make it fit the room easier. Where she is laying, I have put down to pillow cases and then a small area rug just in case she gets any bright ideas at night about digging.