(place holder for forum discussion)
OK Grab your 5X Loupes! If this is your first partial overlap test, you may like it alot! I love it and I think it is the PROPER way to do 3D.
This is the original image I stole from Google
If you resize this to 13.5cm horizontal, you can have a good 3D view holding the loupes straight.
This is a partial overlap image ~50% or so. Probably, I didn’t measure.
This image is 21cm, allowing for an IPD of just shy of ~6cm.
Line up the lenses as normal, get them in focus so the white line splitting the eyes is only JUST not visible then rotate the lenses outward a bit to blend the images. BAM! How cool is that ? Higher FOV for free.