UPDATE: My modifications to the playpen are done!
I will test it out tomorrow. Previously, she wouldn't get out of her pen unless we were gone. We tried putting her in there and hiding, and could never get her to jump out. However, the second the garage door closed and we pulled away, she could climb out! A smart little one she is!
Here's the story on my modifications- the plastic was way more expensive than I thought, so I bought smaller sheets. They start 12" up from the bottom, and go to the top. I think it's better that way, as then the bottom is still open for her, but she won't have anything to get her paws on to climb up. Everybody I told about this said "why don't you just get a taller playpen", to which I would always respond "if she's going to climb 30 inches high, what's to say she won't climb 48 inches high, and possibly hurt herself falling or jumping off??" Unfortunately, we don't have a good room to close off for her to stay in... and she licks everything! So we feel better with her in the playpen.
If it's effective in keeping her in there, I'll post a how-to article. However, the project did take me a lot more time than I thought, but being an engineer, I can't resist a good project

Plus, it only cost $35 which is about what I wanted to spend.
In the pictures, it's very hard to see the plastic. This stuff is CLEAR! The glare gives it away, though, and in the detail shots you can see how it's attached.
Let me know what you think, and hopefully I'll have good news to report when I get home tomorrow and she's still in there (crossing my fingers...).
Later,
-Pat-