I understand your feelings about a big dog and a little dog. I have a 57 lb mixed breed and a 9.5 lb yorkie. They play fight all the time. We worried at first that Carly would hurt Molly since there is such a difference in size. But to our amazement and delight, Carly has turned out to be very good at judging her strength when fighting with Molly. Carly gets down on the floor and they do a lot of posturing, but no one has been hurt yet. It is funny to watch.