I understand that some of those Breeders/Trainers for some larger animals (not Yorkies) who train the Dog to Attack and bite, have found that the length of their tails, has an impact on how mean they are.
The Trainer just cuts off a little at a time, and watches to see how mean the Dog gets. Some use a Cleaver, others use Pruning Shears, but the most handy (I hear) is a large Bread Knife. Just get a block of wood, and whack a little piece off at a time till it's just right.
