[VixTD]

 gordontd, on 2016-November-16, 04:33, said:

I would probably go for 20%, considering that to be "sympathetically weighted" towards the non-offending side.

WellSpyder considered this weighting about right, whereas NS's team captain thought it was closer to 50-50. I opted for 50% of eleven tricks and 50% of ten tricks in the end, as that included a sympathetic weighting in favour of the non-offenders. (There were no naïve players in the first team to consult as word had got round about the pending ruling by this point, so everyone knew which teams were sitting NS and EW, but I trusted my two captains to give honest opinions.)

Is the reason you think a diamond return is so likely even with the correct information that North is much more likely to have five spades than four for his raise to game?

[gordontd]

 VixTD, on 2016-November-16, 12:31, said:

Is the reason you think a diamond return is so likely even with the correct information that North is much more likely to have five spades than four for his raise to game?

Yes, and that their leading method makes it impossible to distinguish whether the lead is from four or five, and the double of 5D suggests a diamond switch.

[jallerton]

 gordontd, on 2016-November-16, 14:02, said:

Yes, and that their leading method makes it impossible to distinguish whether the lead is from four or five, and the double of 5D suggests a diamond switch.

Does it? Surely if holding a 5-card spade suit with ♦A/K he should be leading a higher spade as then he should know that a second round of spades will not be standing up. This leads to a familiar question in MI cases: is it relevant to the ruling that the player's defence was incorrect even in the context of the information supplied at the table?

[lamford]

 jallerton, on 2016-November-17, 15:09, said:

Does it? Surely if holding a 5-card spade suit with ♦A/K he should be leading a higher spade as then he should know that a second round of spades will not be standing up. This leads to a familiar question in MI cases: is it relevant to the ruling that the player's defence was incorrect even in the context of the information supplied at the table?

Yes, and it could be argued that he should also be leading a high spade when he has the ace of diamonds and a low spade when he doesn't have it. That accords with leading a high card when you want a switch. I think 50% of beating it and 50% of not is reasonable.

[barmar]

 jallerton, on 2016-November-17, 15:09, said:

Does it? Surely if holding a 5-card spade suit with ♦A/K he should be leading a higher spade as then he should know that a second round of spades will not be standing up.

Their lead agreement was described as "the lower the spot card, the better the holding in the suit". Nothing about whether they want the suit returned, it seems like it's just intended to help partner judge where your values are.

Admittedly, sometimes you may violate your agreements in order to induce partner to defend differently. E.g. if you normally lead K from KQ, but want partner to overtake with his ace you might lead Q.

[VixTD]

 barmar, on 2016-November-18, 09:52, said:

Their lead agreement was described as "the lower the spot card, the better the holding in the suit". Nothing about whether they want the suit returned, it seems like it's just intended to help partner judge where your values are.

Admittedly, sometimes you may violate your agreements in order to induce partner to defend differently. E.g. if you normally lead K from KQ, but want partner to overtake with his ace you might lead Q.

I didn't ask NS about this, but it did occur to me, and I assumed that they would deviate if necessary from the description given just as anyone else playing any other methods would.