Hmm, all the eye focus does is focus the eye on the crosshair... the parallax is the thing that moves the focal plane of the focused image on the same plane as the crosshair, so the two cannot slide apart when you move your head when the scope is paralaxed to the correct range... so really, altering the ret's focus should not have any effect on parallax, because the difference in focal planes between the ret and the image is still the same, and a function of the lenses in front, not behind.
However, i have noticed that changing the fast focus on my custom shops has a magnifying effect on the picture... in extremes there is slight, but definate change in the size of the picture/ret... it's small, but noticable... i think it's too small to be noticable on POI shift in wind... but it's there... dunno, have a look at that. I haven't looked to see if it affects the amount of relative parallax error, because for FT the scope is always pa'd to the range... but it might be interesting to see if that can exaggerate that.
But i find it odd that you've not got the hairs focused to their optimum anyway... is there some secret reason for this? It's just that the eye will try and dive to focus on the best image, so if you have a weakly focused hair, and weakly focused image, it can jump to the image, and make the hair go out of focus... if the hair is focused better it prevents this to a greater extent.
BFTA/NSRA County Coach
CSFTA Chairman/BFTA Rep