In response to my own post:
I’ve got it all “working” now, and it’s amazing, despite ONE HUGE CAVEAT (which I will explain later).
The joy cons must be attached to your FOOT. This is because the rotation should be expressed on your foot, and from rotation information from moving your foot, not your shins. This means that the virtual SteamVR trackers MUST be at foot level for this to work (i.e. when you are in steam overlay, you should see the trackers at floor level!).
In addition, you MUST have a good Bluetooth connection, or else the rotational data will not be 1:1 with your movements (i.e. It will skip frames of rotation with a bad connection, and you will end up with messed up rotation).
The big caveat that I mentioned earlier is the fact that many Joy Cons have gyro drift, at a hardware level, so you MUST find a pair of Joy Cons that do not exhibit any drift. Otherwise, your feet with the affected Joy Cons will drift slowly 360 degrees in a circle in the direction of the drift.
I experienced gyro drift on the Nintendo Switch using the Joy Cons, so it made sense that it would exhibit that behavior using it in this manner with D4VR.
Hopefully, though it is not an *immediate* issue, it would be nice if Greg can implement some way to counteract this drift — Nintendo does this software side, as you must set the joy cons down flat for it to “calibrate” and get rid of drift.
For now, however, I’ve created my own pair of “VR shoes” with joy cons embedded, and while I have to reset it with a long press of the home/capture button periodically, it allows for turning your body without your feet following your head rotation, which brings the whole D4VR experience quite close to the vive puck system, at least until we can use two kinects to provide back coverage (which may not be necessary if everyone has some sort of rotational instrument to provide data to the driver).
Greg, if you see this, please add the option to add rotational data to hips in normal “skeleton” tracking (and not only in the colored experimental tracking). I believe it’s meant to be implemented, but there is no “hip tracker” replacement in the device manager. This forum post details this issue: https://www.driver4vr.com/forums/topic/hip-tracker-not-available-in-device-manager-trackerhips/
Again, thanks for all the work! ^^