I don't think it really matters inre. to double vs single barrel accuracy unless you are talking about a shotgun used for deer hunting with slugs. Although I killed my 1st deer with a Fox 12 ga double I would certainly NOT recommend this as a good choice.
I've alway shot with both eyes open and tracked the target either a live bird or clay and IMO have only been remotely aware of the fact that I'm swinging a gun either a single or double. The "image" I have is there's something swinging in my hands that is tracking the target just like my eyes and when everything "looks" right I'll pull the trigger.
Jim

The 2nd Amendment IS an unalienable right.