Works great stuck on the marker wand and floor level for head alignment with cross hairs. I think its easier to get better coverage when you have a head in the viewport other than your own.
i brought a three marker wand specifically for the face volume. But its too big and cumbersome for such a small space. So, tell me about your mini wand. I currently calibrate using a small single marker... Sat on the floor whilst watching the monitor thats mounted between the front cameras.
The mini wand, is two wodden sticks (3mm dowel) glued together in a T shape.
Then I put three little 3mm facial markers on the end, 2 of them 140mm appart and the 3rd center dot off center lets say 110mm in I think, I just scaled down the large 3 marker wand.
Then in the calibration section, I use my new calibration distances (not the large wand) and I get green lines galore.