So how big a bomb do you want?

[LurkerBelow]

I would have thought the hardest part of an underground bunker would be through the roof. Wouldn't it be smarter (and what Barnes Wallis originally designed the Grand Slam to do) to actually miss slightly so that the bomb penetrates the softer ground next to the target and the explosion effectively is directed at the sides of the bunker. My recent experiences of earthquakes suggest that a sideways shake is very much harder to cope with (imagine desks, racks and cabinets being flung sideways across a room)

[Rosevidney1]

I agree with LurkerBelow. We have become fixated on hitting the target when a near miss is quite likely to accomplish the desired result.