Virtual arrow with multiple tracking lights

[Vmichaeljin]

I'm not sure how to explain it. All I know is that the rod starts pointing up vertically, even though the lights are horizontally spaced at ground level. Physical rotation does not correspond to virtual, and the rod resists rotation away from the vertical axis.

It would help if you had code that took data from two trackers and rendered an object's position and orientation in a way that made sense for an object like a sword, arm, etc.