Billy is a big boy, and has a barrel chest, so the pupia harness works great for his build. If your baby Gracie is not prone to being startled while out and about then it should be ok. My other cat vindaloo, can back out of the pupia harness if he wants to. My all time favorite secure harness is made by met pet, and is called the cat walking jacket. Hope that helps, and good luck with Gracie and her harness training.