Why would you want to put ghost ring sights on a shotgun that will be used at 'point and click' range?
The fastest shotgun I have in terms of target aquisition is an old 870 Police with a bead front sight.
My new 870 Tactical and my Benelli M4 both have ghost ring sights and they are a PITA. Sure, they're great for slugs at longer distances but it's tough to claim self defense at 50 yards. Besides, at those distances, I want to use a rifle.
Even at 50 yards, a bead sight will still get a slug on target.
Just because ghost ring sights are 'tacticool' doesn't make them practical.
Think carefully about your actual application before you get too far down the road with ghost ring sights.
"No matter how cynical you become, it's never enough to keep up." - Lily Tomlin