There is no answer here for that question.. It all
depends on how you develop your swing.. and your style of shooting.. Do you pull thru..and shoot quickly.. or measure the lead..?? Do you float targets.. or cover them up..????
As PeraziBigBore said, there is no answer to your question. It does not matter whether you shoot with both eyes or one eye, POI is entirely and totally a personal thing. You have to set it where it works for you, and it does not matter one whit what works for some one else. There is no best, or worst, or anything in between. Only where you are comfortable and targets break for you, whatever the POI turns out to be.
The problem of cross-firing is really separate from any issues of POI. This is usually caused by a change in eye dominance (i.e., if you are right handed and your left eye becomes dominant. In such cases, you really have two choices to correct this. One, you can become a "one eyed" shooter, closing or covering the left (dominant) eye, and letting the right eye continue to be the sighting eye, or you can choose to use one of many devices on your shotgun which prevent the left eye from seeing the bead (these are usually stick on "blinders" for the rib, or something like one of the tunneled bead set ups which only allow the right eye to see the bead. The advantage to these devices is that they still allow you to keep both eyes open, but do help prevent the left eye from dominating the "sight picture" and throwing your aim off. No change in the guns POI should or would be required in either case, as long as you were on target before the change in eye dominance. Of course, you could also learn to shoot left handed to match the new dominant eye, but that is very difficult for most right handers, and might not work out in any case.
I would not worry about 1 or 2 eyed shooting until I was sure that #1 you are NOT bead checking--#2 your gun is actually shooting where you think it is, maybe you have lost (gained)some weight--changed ammo-reloads-different choke tubes- extra clothing (winter) or any one of a dozen other things. Try practicing mounting your gun dressed as you will to shoot, visualize a trap field & your normal hold, mount your gun with your eyes closed then open only the eye over the bbl. to check that you are looking straight down the bbl. & not off to one side. If you are off to one side try to determine why, maybe have a shooting pardner watch to help, if you find something there,, work on correcting that. Try this practice routine many times until it becomes automatic & comfortable, maybe 25---50 times a day (night) for a week or at least a few days before you shoot the next time. Don't rush-take the same amount of time between practice mounts that you would have when shooting on a full squad so you don't get tired. But change only ONE thing at a time when you shoot, if you don;t find the right thing the 1st time try something different next week. Usually if we (shooters) just slow down & go back to basics we can find & correct our problems. And as Pat I.says DON'T ASK ME HOW I KNOW THIS---LOL Ross Puls
I shoot with tape all the across my left lens and keep my left eye open. My POI is 21" i kept raising the comb until i was making smoke and still able hit flat targets. I hold 15-18" over the house for 16s on the house for 27yrds and 12" over the house or so for doubles. My scores have been up and down the past couple years due to weight loss/gain/loss. Hope this helps Steve Wolf
Shooting two eyes I seem to need a gun that shoots a full pattern high. let's say I grab a BT 99 off the rack with a regular stock no adj comb. two eyes open I won't hit a damn thing with it. Same gun shooting one eye I can break'em no problem. Not sure why...