David, thanks for your thoughtful comment - there's nothing to be sorry about correcting my mistakes :)
I went back to look up the mathematical basis behind vacant spaces and you are right - vacant spaces theory for suit breaks combines the "suit break in a given suit" and "breaks for all ...
Isn't the point of the decision after South played a heart and West followed low, rather than before South playing a heart? In addition, at this point we know each player has at least one diamond, so that changes the number of unknown cards again.
At this point West ...
Good points - Thanks, Richard. There shouldn't be a keycard ask with a void, but you never know.
I will admit that as partner regardless of which club spot my partner led I would try cashing the Ace of diamonds on trick 2.
NS hands -- http://bridgewinners.com/article/view/atb-unexpectedly-slammy/
(Partner's hand is KQ52 / 86 / AQT9543 / (void) -- so 6H can be set for -500 by under-leading the ace of diamonds on trick 2 but in practice the score will be -200).
I agree that failing to raise diamonds (as most have ...