P-61 Black Widow

[KJ_Lesnick]

I know the XP-61/YP-61 was designed to a British specification that was later cancelled, though I have no idea when this was done; I also know the P-61A & B differed in a number of details which owed to operational experience in the field, and know that the early P-61A's didn't have a turret most of the time because of issues with airflow problems: When the P-61B's were fielded, some could use a dorsal turret, though the demand for the fire control computer would ultimately lead to the turret technology being forked over to the B-29 program.

I'm curious as to the following

• When did the RAF cancel the order for the P-61
  
• Since the early P-61A's turrets created buffeting (which was later curable); they created drag regardless of the configuration used on the P-61A/B, and the DH Mosquito NF's had no turret whatsoever and did fine: Would it have been a smart idea if the P-61B was designed with no turret at all, and used some kind of P-61E like canopy layout?
  
• Would the latter have had a significant effect on production if the turret was removed by the end of the P-61A run totally?