I play butterfly quite a bit, and recently some of the better guys have started doing the headstand pass where you overhook both legs with your arms, plant the top of your head by the opponents hips, and then do a headstand to hop over the butterfly hook and land in side control. This pass is like a cheat code to my guard, and I have not found a good defense yet (aside from trying to keep them from getting the overhooks and head position they need). Any thoughts on useful defense strategies from here?