411A:
The Slowbacks were 11% down in predicted performance in all respects (height, speed etc etc). The Fastbacks were back on specification.
The problem was the amount of drag created by the shape of the rear fuselage. The Slowback fuselage came to a very nice point which looked good aesthetically but turned out to be an aerodynamic disaster.
So the design team went back to the drawing board and re-designed the entire ar*e end. This terminated in a blunt shape but, more cleverly, two vertical strakes were fitted underneath the rear fuselage.
These strakes were of a high-speed elongated diamond aerofoil section.
When we used to go to Lockheeds in Atlanta to pick up replacement C-130 centre sections (they won't go in a C-130) to take to Marshall's at Cambridge for fitting to RAF Hercs, some chaps from the Lockheed design office would sometimes come out to look carefully at the Fastback rear end solution.
I believe one of our crews was told by one of them that Lockheeds would have liked to have used this solution on the C-130 but Short Brothers had taken out an international patent and it would cost them a lot of money to use the idea. How true that is, I don't know.
In-flight refuelling:
I only know of one of my colleagues who ever succeeded in making contact with a tanker during trials. The system was never used in anger. The biggest problem was that the standard high-speed drogue basket went round and round in three foot circles at Belfast speeds so the tanker had to be fitted with a special low-speed drogue which was useless for everyone else.
The second problem was that we had to land after 15 hours or so anyway to check the engine oil so there was not a lot of point in being up there for longer than that.
However, the refuel probe was a great bit of kit if you were flying from the right seat for it was great for pointing at runways and assessing drift!
The whole refuel kit weighed about 1,200 lbs. Surprisingly, our lords and masters didn't start taking them off until 1975.