Dave -
That's still pretty small by the standards we recommend on here. Like nonamian_girl suggested, check out the home page on
http://www.cavycages.com for easy instructions to make something a bit larger (30"X36" or 30"X50") for 2 pigs. Are you measuring the inside usable space or the outside of the container?
Now the next question, is are you feeding your two adorable piggies? I highly recommend cilantro over parsley for starters. Parsley is a lot higher in calcium, and might eventually lead to stones.