I agree with WH, if your eye goes below the rib its most likely a miss on that target, I find one way to get the minimum "flat rib " view is to check the mount on to an imaginary incomer ,this is best done out side,and helpfull if you have telephone or power lines to alingn the imaginary target, mount/swing as per normal along the line, and when you get vertical or just past you have no option but to have you face crammed into the comb, now close the left eye and check what amount of rib you see. its not the one and only method but is a handy check for high stuff.