I do not have an answer to your question I did, however, want to mention that if a person wants to steal your dog they will find a way to do it regardless of how much the dog guards. They can use tranquilizers and they can use the dog catcher's loop.
It's best to have a secured back yard. Some members have security cameras and electrical fences to keep unwanted persons out of their yards.
With today's new thing of dog flipping and the old thing, dog fighting, our breeds are good candidates.