Currently I've got an older female English Bulldog, a pair of adult Tosas, and a female Tosa pup (their daughter). I am the only boss, none of the other dogs are allowed to exert any dominance over the other, unless it's a play thing. All toys are mine etc. My female Tosa and English Bull have squabbled over toys or food a couple times, but nothing a good strong yell couldn't part. I figure there may be friction between my two female Tosas once the pup is mature. Introducing only pups into an existing pack, fixing dogs at the appropriate age, LOTS of exercise, and being a good boss will all help. Would be a good idea to take turns locking away same sex individuals when you're absent, and keeping dog spray around in the event there is a serious fight.