You dont necessarily have to cross to a plott x bulldog. There are some plotts out there that are as gritty as a lot of bulldogs. I know becuase I have one.
I believe it but on average a hound is never going to have the same tenacity as a well bred bulldog, just like on average a bulldog will never have the nose of a plott. But there is always exceptions. How big is your gritty plott? Does he have a good nose too, does he strike on his own. Just curious.