I'd assume a jackrabbit distress call would match pitch on the larger snowshoe hare better than a cottontail distress.

Honestly, I'd say the SOUND isn't nearly as important as the emotion of the call. One of my most productive calls is a Verminator Syco Tweety (or Twisted Syco), which doesn't really sound like any specific animal, but DEFINITELY sounds like SOMETHING DYING brutally, which ultimately is all that matters.

So I'd say grab a Primos Double Jack Rabbit Distress call and try that.

You might also try fawn distress or bird distress. I've never had much luck with fawn distress (and never used it much either), but certain times of year, I hear it's quite productive. Bird distress can work very well. Learn to play a woodpecker distress and you might try that. Small, shrill, high pitched rodent distress is another option.

Frankly, again, the sound itself isn't as important as how it's played. The deeper pitch, the larger animal it usually represents, which represents a more difficult target for the coyote.

One interesting tid bit you might consider... Freshly fed coyotes are not often responsive to a call. Try scouting a bit and just listen. If you can find out when the dogs are socializing (serenading) and moving, then think about when they are HUNTING. You'll need to be calling either before their hunts, or significantly afterwards so they're hungry/interested again.

Another thing I would say. Stop educating your coyotes asap. If you're calling the same spot with the same call 7 times and nothing comes, they'll likely NEVER come. You've taught those dogs exactly what your call sounds like, and gave them good reason to continue to ignoring it.

Another sound you can try this month, since it's mating season, is female invitation howling. You can even use a male response howl to immitate an intruding male taking interest in the female response to further encourage a local male to investigage. I tried the Primos Female Whimper call last breeding season, seemed to work well enough, but took a lot of work bringing them in.