Waist can go as thinner as it can be don't push it or you might get pain or something else.
I actually workout the wider hips more curve firm by padding with a half football of foam sliced in half one each side..one tip starts from the same level of the bellybutton or exactly where your elbow reach along the sides of your belly to tge hip and continue with a extra padding to the upper tight to make it even.
The point is to bring your hips a little as 2 inch wider than the shoulders.
The wider tgey are the biggest ass you need to develop.
In my case i need two halves of sliced foam football along my sides two pieces in the front to hide the bulge. Two buttons enhancer panties and that will do the
trick.You need time to play and model...use the shaping underwear and corsets to shape your 8 shape.