TargetTalk

I have caught myself using/looking through different areas of my glasses; moving my head and or eyes. My coach suggested perhaps trying an iris left a bit open, not stopped down to increase dof but just opened up enough to give me a more consistent sight picture/head position. I "made" one to play with by taking a fairly clean (not perfectly round) 4.5mm pellet hole, cutting it out and taping to the optical center of my lens. Initial testing gave me pretty decent grouping albeit 2.5 to 3 rings lower than without it. Is this "normal" from an iris? No problem to adjust sights but I didn't touch them just to see what would happen and when my hold was pretty respectable and with a smooth trigger release my poi was consistently lower.
Fwiw, looking through 4.5mm did of course not greatly enhance dof but seemed to make the target a little more blurred and front sight not "sharper" but somehow more "isolated" in the sight picture from the target. This did give me improved trigger release, easier to keep eye on front post & follow through.

My aperture is open about 3mm.

As far as the shift, it is common to have a poi change with different light levels or where you are looking. Focusing on your front sight vs on the target will change the poi.

If you had three people shoot a pistol claiming an exact 6 o'clock hold from sandbags, you would have 3 wildly different groups.

If your groups tightened up, then you had a positive outcome with your experiment. I would try some different hole sizes to find what works the very best for the ight you have available.

Different front sight widths, and rear sight gaps, will also change your poi and perhaps could be played with. Sometimes little changes sync with your brain better than you might think. I worked with my sight gap so that holding halfway down in the white corresponded to an even amount of white on each side of the sight, and that same amount of white up to the bull. I think that helped me.