i spoke to bullyveiw today who are one of the top breeders in the uk ! They told me that allthough that its not ideal and it would be better if his jaw wasnt undershot ! he could still be used as a stud dog as long as he was bred with abitch whom had a perfect bight! They all so said that you can even have a bitch and a dog with a perfect bight that will produce undershot or overshot pups! the world is not allways even!