acamper , i have just joined but have years of experience with lgd,s specifically mastiff type,s i currently own a 9 year old bullmastiff girl from one of the only kennels left to breed bullmastiffs true in the sense of what they were bred for protection be it estate or family.she had a litter 4 years ago two of her pups went to an ex army dog trainer whom had won awards for training ,agility etc i recently bumped into him asked how the dogs were and he explained that in his 40 years of training he had never come across a dog that could spend years learning commands understood them carried them out under normal conditions repetitivly many times yet still when out of training enviroment would not respond in anyway other than to stop whatever the dog/s saw as a threat.my girl is 9 yet goes from 0 to 30mph in 0.5 sec weighing 110lb basically what line you get the history of the kennels breeding either showing or for true type etc will effect your efforts , i know somebody who has a 130lb bullmastiff which would not bite or pin a burglar it so happens to come from show lines to me this is a dummy not a bullmastiff would you buy a ferrari that only did 70mph .my experience with dogs such as filas , co,s and the like is you cant have your cake and eat it but that is my opinion and nothing more it seems though as you are putting a lot into educating yourself firstly if more did this then we as humans wouldnt have given some breeds the bad press they get good luck mate hope all go,s well.