The foregoing was the official procedure, especially as Mk 2 ballistic computer lower limit was 17 000 feet. The Mk 1 computer lower limit was 7 000 feet. Some Mk 1 crew used the ballistic computation and achieved much more accurate results in training though some reached the automatic bomb release point when they were too low, 8 900 feet or so.
Subsequent research years later (book due out next year) showed that research branch said that much lower release heights could enable weapons function and sufficient time for successful escape.
Two final points related to the previous post. To achieve the 15 degree pitch angle the attitude instrument was modified. And to achieve accurate timing for the rotation the Navs Plotter were issued with Lemania chronographs. It was not long after that Navs Rad were able to blag them too.