If you have 3dof tracking only, consider making the displayed image to have no stereodisparity, this way it is optically correct to being a screen projected onto the celestial sphere. This is also how reflex sights works on fighter jets and guns.
I've been thinking about combining it with our work on the reverse engineered HTC Vive Ultimate Tracker stuff here https://youtube.com/shorts/U4vhEPQw-Uo to get 6DOF
But realistically I ( and nobody else ) won't strap the tracker to my head all the time