I have used whippets and 3/4s for years on foxs, but never one out. I run them with a finishing dog usually one of my apbt, the whippets job is to slow them up thats it, which most I have trained will do.
I don’t run them often enough these days, and haven’t for over 20 years to justify a designated dog for this, or I would have one, bull x dh/grey was my dog of choice. There may be a few whippets that can and will kill them but not many, out of ½ a dozen Ive owned only one ¾ whippet x DH was capable and still struggled. jmo
PS never seen a whippet that wouldn't chase a bunny