Thanks Jerimiah for getting us started here. You have the right idea, getting out on one leg. However, we need to remember iliosacral motion is relative motion. That is, all the bones of the pelvis are moving in the same direction; but, one is going faster than the other. In this case, the motion is driven from the bottom up, so the L ilium is going faster than the sacrum in a counter clockwise fashion.
What I'm getting at is you have the right idea of going after the core, but we need ground reaction force to get the right chain reaction biomechanics going on in the pelvis.
Jonathon, you & I are thinking along the same lines. Use the same side arm to turn on the abs to keep that ilium from going too deep into the zone. I chose a LLE posterior lunge c/ a LUE posterior @ overhead reach. I realize you chose an anterior lunge. Who is right, me or you? Or are we both right- or both wrong? I will have to consult with Marty Lambert on this one. He is a functional P.T. with a background in osteopathic medicine.