Acol, 3 weak twos, weak NT:
South finds the low club lead and they take the first three tricks.
I was West. My plan was that bidding 3♦ on my second turn establishes a game force and if partner bids 3♥, I can bid 3♠ to show delayed support, then we might find a good major suit slam. We however end up in the hopeless slam. My interpretation of partner's 4NT bid was RCKB in diamonds, although it is debatable whether 4NT here should be RCKB or quantitative. The problem seems to be that the way the auction has gone, I cannot show a powerful hand with secondary spade support. Can you suggest a way to take this a bit more slowly and advise on whether there are general rules on when 4NT should be Blackwood and when it should mean something else.