Perhaps I missed it, but nobody seemed to mention any advantages regarding the blast.
I would personally like to play blasts like these as an attempt to hide as much information as possible, hoping that superior contract doesn't exist and that I'll be able to get a favourable lead.The extra overtrick that you gain from it would mean the difference between a top and an average. However here 6NT and 7
♦ are still possible contracts so blasting seems like a bad idea.
First of all, unless you have some ways of uncovering a 4-4 major fit after an inverted minor, I don't see why you should reject trying for a major fit. Isn't this matchpoints after all? It's not difficult to construct hands where we can make 7
♠ or even 6
♠+1 where 6NT= is the limit in the other strain. It is only wrong when the combined hands are strong enough for 12 brute-force-tricks while there's a sure
♠ loser(usually due to missing
♠QJxxx). Fortunately, it's still possible to convert back to 6NT once we check upon the missing
♠Q so there's nothing that bad about searching for a
♠ fit.
(Edit : I realised there are some hands where you have both
♦ and
♠ fits, but there's a sure
♠ loser while you can make 7
♦. Something like
♠Axxx
♥x
♦Axxx
♣KQxx. But still, I think it's better to investigate for 7
♠, which is the highest scoring contract if there isn't enough for 7NT.)
Next, if the 2
♣ rebid has been standard (which it certainly looks like), that could be anything between 12-18 HCP.
Give him
♠AQ,
♥K,
♦A
♣K and that's only 16 HCP with chances at grand, and he might have more than that.
Well, you could say that this is unlikely... but even with some minimum hands(say 12-13HCP), a combined hand of 30-31HCP with the 5th
♦ would give good play to 6NT, which is again a better scoring contract EVEN IF YOU MADE 6
♦+1.
If you really need to blast, go for 6NT
On this particular hand, reaching 7
♦ should be easy.In fact once partner shows
♠A,
♥K,
♦A,
♣K after RKCB ace and king ask, we know that his 4 major cards (since he showed 5
♦ and 4
♣) are covered and we have no minor suit losers.
As for 7NT, even if partner has
♠A,
♥K,
♦A,
♣K,that only provides us a good play for 12 tricks, so it appears that the key is to check if partner has extras. Unfortunately, this might be difficult after 1
♦-1
♠-2
♣-?. Depends on partnership methods I guess.
Lastly, blasting at IMPs is simply a bad idea. I've lost lots of IMPs just because I didn't bother to try for an unlikely grand.