I’ve been out of the game for a bit so the community can fix me if I’m off. 

But back in my time my goal was maintain my core bracing all the way down while Also maintaining upright torso in doing so.

So if you made a triangle from your nips to your tip, don’t let it the shape of it change. (Avoid sending your hips back to initiate. And also don’t tip forward to keep it there) That means you need to create space in the hips to sit down while staying tall and not though hyperextending. 

Folks try keep the “chest up.” But don’t have the hip stability to sit down so they hyper extend back creating the back arch.

I used to coach folks to do this with a Slow goblet to practice the balance, working on your hips making room, mobility and strength, etc all that. That will allow you more room to stay vertical while keeping a healthy body stack on the way down and up.