The boot he put in was NOT ment to be able yo hold ther cut together but just to cover any rough spots in casing from the cut. If you look at any boot they are only perhaps a third as thick as the tire sidewall. If he would have done it correctly he would have piut that boot in but then put one twice the size over it and followed up with one 3 times the size. Tire stores do not want to carry any boots big enough to do the job. You needed to tell him ok just go to your suplier and get those 2 extra large boots and put it. Might have taken him a couple of days to get them but her could have, now it may take a lot longer but you get enought total size and thickness and they will work and hold up for years. He may say that many boots will make the tire to unballanced, the tractor is not a highway machine to wory about that. I had that problem and when I saw the mini boot that he was putting in I told him to get a proper sise and he did. And it held up for years.