in the seventies don mayfield sold some pure tudors dibo dogs to keystone kennels wher he still has the mayfield line pure. mayfield also sold some pure dibo dogs to japanese fellows who came here to get them to cross with tosas. most of the matches the pitbulls were just begining to fight when the tosas tired of skin holds , then the gamedogs would get the better and some tosas wer killed before the 30 minute mark for the ring, but the japanese did not like the fact that gamedogs will make noise from pain , and only bred the most silent ones. facts its all documented.