The description of the negative double includes "10+ total points". Eight Souths made four different choices, explained as:
Dbl: 3+C; 15-22 total points
5♣: strong rebiddable clubs; 19-20 total points
5♦: 6+C; strong rebiddable D; 19{the rest cuts off}
and pass.
Is the double a value-showing double, saying nothing about shape in general or spades in particular? Why do we need 19-20 to bid 5♣ when we know partner has 10+?
GIB doubled over the pass, left in South's double, and bid 6♣ over both 5♣ and 5♦. Is there no way to play 5♣?

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