Armen,
You truthfully admit you shoot shotguns little and are not a serious shotgunner.
You truthfully admit you don't know what you are supposed to see over the rib and it seems, as of yet don't know what it means.
Yet many tell you to get a gun that fits. How in the hell are you going to know?
Combine it with the fact that consciously throwing a shotgun up in a store and doing the same unconsciously in the field-the head will probably tend to be more often than not off the stock more-are two different things.
Save the money for now and shoot more. If possible shoot around some who know more than a little and make friends with some of them. Get some experience and acquire some knowledge. Get a feel for what works and what doesn't for you. Which shotguns feel right in your hands; which ones you just naturally gravitate toward.
Then you will have a foundation of what is right for you and if you will have to make any changes to make it even more so.
There is your answer. Most likely not what you wanted to hear but the truth!
As to mounting in a store and with eyes open or closed. Your whole focus doing that is planned out already. Your conscience mind has (for lack of a better word) prepaired for the results you want. Meaning you will not get your natural mount and more then likely an overly exaggerated one at that. Which is going to give you misguided fitting measurements.
If you absolutely have to buy something now, I would say buy the Beretta. Parts, smiths, and resale value are all in its favor. Good luck
