Thanks for the RO, Neil: XG 3-ply [O N26 @38] 9k 5k$. My old Snowie trunc is in close agreement: [O N25 @40] 1t. Judging by the posts in this thread, you're all in good company; 63S-33R-33 is a commonly misplayed position -- as I mentioned here.
Consider the two positions diagrammed above. The first is the basic 63R-33. The second is the trickier 63S-63R-33 (the one you rolled out). In both positions Blue will hit on the 10pt (in one case covering the 10pt and in the other case entering) and the question is whether to make the 3pt or the 5pt with the other two 3s.
All four after-diagrams are shown below, with some brief notes in between.
The following three swings help explain why it is correct to make the 3pt in the upper right yet by contrast it is correct to make the 5pt in the lower left:
- White's 62 plays worse in the upper right (where there's nothing to hit) than in the lower right (Bar/23 13/7* is available); that is, leaving the 8pt blot is less costly in the lower left than in the upper left.
- White's 32 plays worse in the upper right than it plays in the lower right (Bar/23 6/3*). Blue's gain is greater keeping White from anchoring with 32 in the upper right than in the lower right.
- The cost of allowing double 5s in the lower right compared to the upper right, is less than the cost of allowing double 3s in the lower left compared to the upper left.
That's a good head-start. I believe the rest can be mostly explained by the heightened value of owning the stronger point (the 5pt) when there is an exchange of hits and such exchanges are more likely to occur in the diagrams below than above.
Nack
