How many centimeters (or inches) can be added to the hips during a BBL?

When I was younger my hips and butt were round and full and my waist was tiny. Despite being the same weight, now my fat has collected on my midsection and my lower body isn't full and round anymore. I'm thinking about a BBl to correct this but they seem focused on achieving projection and that's not needed. I'd like a flatter stomach, smaller waist, full round hips (very important!!!) and a perky round butt. Is a BBL right for me, and how many cm can I realistically expect to gain on my hips?