Oh, Im sorry.. I missed that..
Yes, my Yorkies all weigh around 5 to 6lbs. But... I have sold many of my harnesses to larger Furbabies and Have only heard good things. I even have a lady with a pug and she only uses my harnesses. The only way that I know that the harness comes undone is if the velcro was not attached straight when the harness was put on. Other than that they hold "very" well for all sizes..
How big is Kacee?