Anna,
Have you checked with any Mastiff (I think that's Bon's breed) breeders. Perhaps if you find a breed club and get info from some other owners of the breed, it will help you formulate your opinion. Here is the link to the AKC site. AKC Mastiff website This page also has links to the breed parent club and some breeders who may be able to help in the decision. I only know about what's best for Goldens. Sorry