The rear headrests on he Model X is smooth and they are not adjustable. Has anyone attached a mirror for their rear facing car seat and if so can you post advice or a picture. Mine just slips off and is intended to be mounded on a seat that has adjustable head rests as there are vertical straps that go around the head rests (which don't work on the Model X) and horizontal straps (which do work on the Model X but aren't enough to properly secure the mirror.)