I am not sure if this has been discussed before. If so, please forgive me.

I am wondering what is the suggested height for the Xpen? I purchased a 24inch one. My yorkiepoo is 3 months now. But, I am not sure if she's going to outgrow it. Right now, she's not showing any signs of being a jumper. But I dont know if that will change in the future. The cashier told me that I could bring it back if I didnt think it was going to be high enough. I havent left her at home alone (for a long time) in it b/c I fear that I am going to home and find that she's weazled her way out of it!! (I could just be paranoid!! LOl!)
I am just wondering what size Xpen other members have?
Last question, I put a painter's tarp (as suggested on here) under it, but it seems to make it slippery, allowing the gates to be easily pushed out when she touches the sides. Any suggestions?
Thanks in advance!