Hi Zennie, I'm not sure about fitballs in particular, but I'd think any position where your legs are apart to encourage your hips to widen would be good. I've heard bouncing in that position can be good? *Someone correct me if I'm wrong there!*
Also, if you sit (on the ball or otherwise) and lean forwards against something (I used to do this straddling a chair and leaning against the back of it) again with your legs apart, this will encourage bubs to face towards your back.
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