The young cottontail distress sounds very realistic and is quite similar to what I try for with a mouth-blown call.
http://www.western-rivers.com/downloads/Cottontail%20Distress%20Young.mp3
I don't know your location, but here a sound similar to it will work well on foxes. I learned the call from a cat. He had captured a young cottontail and was "playing" with it. The rabbit would emit a series of screams then slowly calm down and be quiet. After a minute the cat would release & re-capture the rabbit and it would repeat. I sat back and listened carefully, the a couple days later took a mouth-blown call and headed for the woods. I tried to copy the sounds as best I could and had a red fox almost run over top of me within a couple of minutes! Keep the series of screams short (30 seconds to a minute) and put all the distress, fear, and agony you can into the sound at plenty of volume.