i know that the shooter's height of eye, controlled by the comb height determines the POI. What I don't understand is what the rib has to do with it. Seems to me that adjusting the rib height will change the relationship and appearance of the distance between the the front and middle beads but unless the comb is moved, will have no effect on the POI. I know some people seems to think that adjusting the rib is a form of "fine tuning". I can't see that it has POI effect.