I just made a batch with slightly longer COAL, 3.3200". I'm also working more on my cheek weld for consistency. I shoot very well with open irons, but I am still getting used to optics/eye relief.
Keeping in mind this is a cheap old Bushnell, my comfortable and repeatable cheek weld so far puts the crosshairs off center, with a lopsided black halo around them, if that makes sense.
Now, if I sling up into a properly built prone position, forcing my eye relief to be shorter, I get a perfectly concentric black halo around the sight picture, and my cheek weld is much more consistent each time I rebuild the position. Unfortunately, shooting groups with a sling is not yet my forte.
These are optics fundamentals I obviously don't have well in hand.