No worries on the red fox, a grey can kill a red. I often set up in transition areas to hunt reds and greys(edge of the woods near field). For years I have used red fox pea as a cover. It makes the greys madder than a mashed cat. They come running in looking to whip some red butt. In the past I used a red and grey fight tape, I never had a red come in to help his buddy only greys. If you hunt an area that has bobcat, they probably wont come in on that tape though, may just want the woodpecker by himself or cottontail by himself if you try to target cats.
Good Luck