most low gunners i know have issues getting the gun into the pocket of the arm pit the same every time. yet, they pull the trigger anyway. that would be an example of what i mean by gun not pointing where they are looking.
ribs in my opinion were meant to guide the eye to the front bead so everything else could be used as a reference as to what is lined up right. the addition of the center bead aided in that too. but unlike rifle or pistol, where focus is on the front site, once everything is lined up the focus must change to the target. as gun owners shoot the same gun over and over, the actual need for the rib or sites does diminish, as the gun becomes one with its shooter. thus why many including me, can shoot a game of skeet or trap w/o realizing my front bead flew off. i just bring it up and it fits into my known pockets and stance. and for that reason, rib or no rib makes no difference. time will allow a gun to point for the owner w/o external aids.
hope this helps.
