Tilt tracking was a long, hard process but after 4 years, it finally surrendered.  The best solution ended up dividing the 25 body parts from openpose into 4 vertical zones.  Depending on which zones are visible, it tilts to track the head zone, all the zones, or just tilts up hoping to find the head.  The trick is dividing the body into more than 2 zones.  That allows a key state where the head is visible but only some zones below the head are visible.

The composition deteriorates as the subject gets closer, but it does a good job tracking the subject even with only the viewfinder.  It tries to adjust the head position based on the head size, but head size can only be an estimation.

It supports 3 lenses, but each lens requires different calibration factors.  The narrower the lens, the less body parts it sees & the more it just tracks the head.  Each lens needs different calibration factors, especially the relation between head size & head position.  The narrower the lens, the slower it needs to track, since the servos overshoot.  Openpose becomes less effective as fewer body parts are visible.  Since only the widest lens will ever be used in practice, only the widest lens is dialed in.

The servos & autofocus are real noisy.  It still can't record anything.

All this is conjecture, since the mane application is with 2 humans & there's no easy way to test it with 2 humans.  With 2 humans, it's supposed to use the tallest human for tilt & the average of all the humans for pan.

Pan continues to simply center on the average X position of all the detected body parts.   

There is a case for supporting a narrow lens for portraits & talking heads.  It would need a deadband to reduce the oscillation & the deadband would require the head to be closer to the center.  A face tracker rather than openpose would be required for a talking head.