A proper big bull x is a lot to handle if he is a proper game dog , some people have no need for that size and gameness, in all honesty you don't need a big bull x for fox it's just to much, that's the reason I am going down the route of properly breed bull whippets , 21" or 22" and properly bred dogs will do for foxes, you kept the gameness of the pit but downsize them a bit which makes them just as game at a fraction of the size, in my eyes a perfectly suitable fox dog.