AH has always modeled a 1944 Lancaster with dual .50s in the tail.
There were also 1944 Lancs that had dual .50s in the dorsal turret, but retained the quad .303s in the tail turret. Most Lancs had dual .303s in the nose and dorsal turrets and quad .303s in the tail. Some early Lancs also had dual .303s in a belly sponson turret.