I wouldn't waste a lot of time on this. Visually center to get in the ballpark. Benchrest it and adjust from there. Loctite when you're done if you have tension screws.
I've had multiple Gen2's where, with visually-centered sights, groupings were off substantially to one side. This was benchrested and confirmed with multiple shooters. One of my Gen2 G17's has the rear sight 70-80% to one side to be dead on. That one is ridiculously worn and has had a hard life.
Haven't seen that issue much with Gen3's or newer. For whatever reason, some older ones are real weird like that. Probably something to do with barrel, bore, lug wear, etc.
Point being, you won't know until you shoot it, so don't stress over fractions of a millimeter because it'll probably just change once you shoot for groups.