Francis, a mid bead on a field gun may have been added by someone who shot trap or skeet and simply became accustomed to twin beads on his gun. Then again, missing the target is rarely the fault of the gun - most shooters know this deep down inside even if they don't verbalize it - and once again, the mid bead, even on a field gun, was usually added for that "extra insurance".
Dave, you're certainly right about that! Concentrate on the target and let instinct do the rest.
