Would think in a more modern plane there would be some sort of automatic compensation thing going on?
The Nav Radar would have done all the flying and ranging through the bombing radar. The NBS bombing computer would have opened the doors and released the bombs IAW the sequence selected.
Any aerodynamic effects from the release would be corrected by the autopilot. There might have been a "Cor" from the pilots.
A Valiant was planned to carry more bombs, One of the projects was to have a bomb carrier with 10 1,000 bombs under each wing, (the underwing fuel tanks had a 12,500lbs each capacity). This with 21 1,000 pounders in the bomb bay would have totalled 41,000 lbs still with full (five hours) internal fuel.