(Courtesy of Bob Crosby)
Doubling freely bid slams in IMPS should be lead directly only, never for penalty no matter how badly bid . Why ? The mathematics of the IMP scale dictates that strategy. Years ago the winning pair at a Calcutta bid stupidly up to 7 vul. An opponent had K9xxx of hearts and doubled for penalty. What happened next was the biggest swing of the tournament – the 7 bidders pulled to 7NT and made it for +2240 ! The par result for that board was +1400 for a small slam bid and made. The opponents were about to win +1600 or 17 IMPs instead they lost 13 for a 30 IMP swing !!. If the opponents stayed in 7 doubled they would have received +500 instead of the +200. They would have won +1900 instead of +1600, +1900 is 18 IMPS ! In effect they gambled 30 IMPS to win 1 single IMP. The mathematics of the double makes it a reckless bid.
In this years Calcutta, the opponents bid to a silly 6 slam. You are on lead with xx AKxx Qxxx xxx so you make a penalty double as they are going down right ? Wrong, LHO pulls to 6NT and partner now must find the heart lead. He does not and you lose 13 IMPS as the par is a vul game. You were about to win +750 which is 13 IMPS instead you lost 11 IMPS for switching the lead. Your double of 6 would have netted you +200 or +850 which is still +13 IMPS !! Your double would have gained you ZERO IMPS but you lost a 23 IMP swing. The double was just an atrocious bid.
Maurice and I had a Grand Slam Force screw up the other night and ended up in 7 off the diamond Ace. RHO doubled us in 7 for penalty. Again this is a horrible bid as 7NT makes on this hand. RHO held xxxx xxx Axx xxx and does not want a club lead .
x Kxx xxx AKQJxx I pull to 7NT and LHO is on lead. If a diamond is not lead I get 3 spades, 4H and 6 clubs for 7NT making instead of 7 going down. What if I had another diamond and the board another diamond ? Partner is void in diamonds and can not lead a diamond and 7NT makes! Again the mathematically folly of the double is displayed by the IMP scale. You win no IMPS for your double but you could have lost a huge swing in 7NT.
AKQx AQJ10 KQJxx Void
What if you had a void in clubs against 7 ? Should you double when you could possibly push them to 7NT making ? There is some debate on that but my feeling is that you should double anyway. There is no guarantee that they can make 13 tricks in NT and the lead is going to defeat 7. There are no certainties in bridge.
Stan Cabay had KQJ9x of spades at the recent Calgary regional and Nick & Klimo bid up to 6 spades. Stan did not double 6 as it was IMPS and 6NT might make. He later said he might have doubled 4 but never 6. There is a lot of logic in that statement !