Given the possible precision I like the idea of a bomb queue. Same as the Upkeep rather than Grand Slam that simply pulverised the whole area.
The Tall Boy was, I believe better on the submarine pens as its casing was stronger.
The Impact Velocity of the TB and GS was only 1020 fps assuming a release at 20,000ft.
From 40k a TV of 1600 fps would have been possible.