first we must realize, if we dont already, that spine angle is kept in the lower back, not in the middle or upper back. Spine angle is the relation of upper body to lower body where they meet.
First we must set up right, bend at the waist. Now have you heard about sitting on a bar stool and other things like that? we need to get the hips into the correct position. take your hands and place them on your hips like you are going to square dance. Now take your thumbs and push the upper part of your hips towards your stomach while pulling the bottom part of your hips back and up. Biomechanically speaking this will help lock them into place

now make practice back swings while feeling that position we established with the lower back and hips at address
and now let the discussion begin