In my opinion if the dog is going to carry the mastiff name then they should be large, well boned. I believe the temperment in the corsi in the US is much different. They range greatly within the breed. I have seen many corsi in italy, they do seem to have a sharper temperment, that maybe due to cross breeding. I know I know, that statement is contreversial but I have witnessed it first hand. Nothing wrong with that, but its just my observation. What I don't like are the slender corsi from Italy.