Thx all.
I think the most important point here is to discuss the objective of a 4NT two-suited overcall. At 'green' you might be tempted to use 4NT both with strong hands and hands geared towards a sacrifice. The price to pay is pard won't be playing you for solid values and you'll miss slams on occasion. At other vulnerabilities most 4NT overcalls are probably better played as strongish hands.
Obviously, this is something you should discuss with pard in a more serious partnership. There is actually a case for having 4NT depend on opps style. Not all people play that a 4M preempt at 'red' should show some defensive tricks. In that case you might want to play 4NT as constructive all the time.
Another consideration is if 4M is done 3rd seat. In this case 4NT can always be of the ambiguous variety (regardless of vulnerability) because pard is passed and won't have much to say except to pick a suit. Also, a 3rd seat 4M preempt might be made on a very wide range of hands, which is another reason for using the ambiguous 4NT.
As for the hands in this case, they were
I was South and actually passed 4
♠, though not because of technical reasons. I passed because pard is an overbidder, who will proper himself to slam at the slightest excuse.
5
♥ is makeable, but it's highly unlikely you fish out the singleton
♣K. In practice we let them play 4
♠ and set it by 1 for a decent score.
You are NV vs V. Do you..?
- Pass
- Dbl (take-out)
- 4NT (two-suiter)