The "Saint Mastiff" is a mixture of Saint Bernard and Mastiff. This is a huge dog. Due to the size, I don't recommend this mix for anyone with small children- just by moving around this dog may innocently knock over a child or elderly person.
This mix has a great deal of coat and does tend to get matted around the ears, and a great deal of coat built up on the hind end. This breed is a fairly heavy shedder but with regular brushing it may be able to kept under control.
Training is a must since this is such a huge dog and she could easily drag you around when walking if not properly trained.
The main health problems with this mix is hip dysplasia and bloat.