HTB,
<<Re the Calc 3 and low level laydown, I vaguely remember having to wind the height down to -500ft. Whether this was to frig the ballistics or to "interface" with the Calc 5 to produce a radar picture which would otherwise consist of a a big empty hole in the middle I do not recall (which is probably why I spent more time on 27 than most!).>>
We did not use ballistic computation for the 2F or the 2J. We would calculate the FT and then fly the groundspeed to achieve the correct values. I think you are right about the height being set for the Calc 5. It was, I seem to remember, set on the CU585 for the Calc 5 as you surmised.
FT for the 950 was about 400 yards and for a 2J at 350k about 1.2 miles I seem to remember.