I have not done it and I do not know what your tractor looks like. Have you considered mobile aprons? I can envision a strip of wood, say a 1" x 4", with about 18" to 24" of wire attached to it. Put some type of stud on the bottom of your tractor, maybe a big nail, a lag bolt, maybe a regular bolt, and drill holes in the 1x4 to fit over those studs. You could set it up to use butterfly nuts on bolts to hold them on if you think it needs it. Or maybe use eye bolts and carabiners to hold it on. Have 4 of them, one for each side and each end and let the wire overlap a bit at the corners.
Another option. Instead of using a 1x4, just cut a piece of welded wire or hardware cloth, put eye bolts on the bottom of your tractor, and use carabiners or snap locks to hold it on. You'd probably need to take them off and put them back each time you move it, but that should not be too difficult. You might want to use a 2x4 or something like that to weigh the wire down especially if your grass is a little high. As I said, I have not done this but I'd think along these lines if I did decide to use dig protection on my tractor. I have not had a problem with anything digging under my tractor, but my dentist had a raccoon dig under his. It is a valid concern, especially on uneven ground where the bottom of the tractor may not set flush with the ground.
I'll subscribe and see if anyone else has some interesting suggestions. It is an interesting question.