I only have one Yorkie but I have a 110 lb Weimer, a 60 lb. Blue Heeler and my Cissy is a whopping 8 lbs. They get along wonderful..... I am amazed how well it works!!
When I brought home Cissy, I would tell the bigger dogs - "easy, easy" - when they were playing. Little did I know that Cissy was going to be the one I should watch - she has no fear and takes no prisoners