Jenny, I just read your post below about Abby not wanting to sit up. You know what I loved with Sophia (you may have tried this) was sitting her up inside the boppy pillow on the floor. That is how we practiced. She was kind of propped up but also practicing her own strength - but if she tried to topple over she just leaned onto the side of the pillow instead of falling onto the floor.
Our phrase at this period was, "Tiiiimber!" LOL.
Re: BritishBride
Positioning Spencer in the Boppy worked/works for us as well.
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It's Beshert