I don't think that they removed the crew member-- I think the wop just doubled up as a gunner. When they took out one of the guns, they lost one of their responsabilities.
Originally the B-17 crew was 10 men. Pilot, Co-Pilot, Bombardier, Navigator, Top Turret/Engineer, Radio-op/Gunner,Ball Turret Gunner.Right Waist,Left Waist.Tail Gunner
Later it was reduced by one man when the radio room gun position was gone so it was a 9 man crew.