One PT had me doing knee to chest stretches too, which didn't make sense because that's the way I could bend. It's the other direction, tailbone up, I couldn't bend. I also read, not sure if it's true but makes sense, that a flat back, or tucked tail, opens the SI joint which can get one in the situation I'm in. I do notice that when I tuck my tail my SI joint starts "talking to me".

My SI gets out of whack about every 6 mos and has to be adjusted so we'll see if this "new" position works.