I agree with you. Our breeder put it in the contract that our dog would be neutered before 7 months old, and he was. She said that the parent dogs' protective instincts were unbelievable, and that it is bred in the bone, no need for any training whatsoever.
And Mastiffs are SMART! Very good at sizing up people and their intentions. We love our mastiff puppy--he is the best, kindest, gentlest dog we have ever had, but we have no intention of being breeders. That would be like taking our lives in our hands, no matter how much they love us. Click on my name to see his pic on my profile page.
I've thought about getting a Matiff, I like Newfs, but I've always thought a Bull or English Matiff would be cool too. I've read that they have very good temperments, certainly if the dog (matiff) was a killer we would be reading about it instead of pit's and rot's.
They're cute! You've got some good company.
I know I wasn't invited but I looked anyway. :)