I had the luck to pick up the monster South hand and was wondering how to interrogate partner's spades... when he opened them himself second. The only question is 6N or 7N, so RKC, and he did have he ♠AKQ tight. Either the ♠J or ♣K will freeze 7NT, but I could only ask (and fail to get) the latter.
So, in the tank, I was constructing some possible hands. The worst possible (assuming rule of 20) he could put down was AKQxx, the ♣J and a 5-suiter somewhere: ♥ gives me a 3-3 break, a 3-2 and the finesse, minors just a 3-3 or 50% (squeeze on ♦?). If instead of the J I get a sixth spade, that's a 3-2 or 50%.
And the decision was to ignore the ♣K completely. Close enough to the business 2/3s or no? And if I chickened to 6N, could partner point to his own ♠J and call that a 13th trick?

Help

North-South
1♠-4NT
5♠-5NT
6♠-7NT
All pass