Source: (an extract of): Preempts with Fit
Partner opens 3
favorable and you have five diamonds with nothing on the outside. An example hand would be 
432
32KJ432
432. Over RHO’s double, what tactical bid do you think is best? Suppose RHO passes.
There is no clear-cut answer to this problem. The opponents could have a hand where nothing you can do will stop them from getting to their best spot. What you can hope for is that the strength is divided and the opponents won’t be able to communicate their extra strength. Most experts raise diamonds with the range between four and seven. Some experts think that bidding 4 will do the job. They hope that LHO will double and RHO will bid four-of-a-major which will end the auction. If RHO makes a takeout double and you raise to 4, they think that LHO will bid a heavy four-of-a-major which ends the auction. Some experts think that bidding 5 will do the job.5 takes away the opponent’s Blackwood bid. However, you show more strength bidding 5 over 5 then bidding 4 over 4. Some experts even bid 6 or even 7.
Most experts think that straight forward bidding is best.
Jeff Rubens—In either case, I bid 4, which makes it awkward for either opponent to show strength. However, bidding a different suit might be indicated if it were known that the opponents had weak agreements in this area.
Marty Bergen—4.
Eric Greco—This is an age old question. In the instance you give, where it is extremely likely the opponents have a slam and I have lots of losers, I would bid only 4 to induce a heavy four-of-a-major bid on my left. RHO with a big hand has to give his partner some rope so will often pass with big hands. For example say LHO has KxxAQxxxxAxxx and RHO has AQxxKxxxAKJ10x. It is very possible this will be the end of the auction where they are on a club guess for seven, and we have seven losers. Now if I think the opponents have a slam, but I have lots of shape and therefore fewer losers, I may start with a 5 or 6 bid with the plan on saving.
If you held xxxKQxxxKQxxx, you could bid more since there’s a good chance that you only have five losers.
Barry Rigal—4 normally works reasonably, 3NT always causes problems. Outright psychs such as 4 or 4 may or may not work. Sometimes bidding your three-card suit works better than bidding your two-little suit.
Alan Sontag—Probably 4. But a case can be made for much higher. Unfortunately any giant preempt will be met by an opponent who will believe you.
David Bird—After a double I would bid only 4. To bid higher may push them one of them into an overbid, which his partner can then raise. If RHO passes, I would try 3NT.
Some experts raise diamonds but also consider bidding 3NT or some other psychic bid.
Zia—If you are feeling really greedy and against underbidders 4 may do the job with a jump to 7 later if it gets out of control. The 3NT bidders always regret their bid, but if you bid 6 they may well bid six-of-a-major, not seven, so if that is your target, it will work. 7 will always get doubled so if the math works, it is pretty safe if you think they are cold for a grand.
Ron Smith—4. My left hand opponent might go low after 4. He’s going to bid.
Mark Lair—4 over the double. Over the pass I’ll bid 4 which is keycard.
There are experts who bid either 4 or 5 depending upon what they had for breakfast.
Kit Woolsey—A simple 5 is generally best. This way the opponents don’t get any free doubles of artificial calls to show strength, since 5doubled might be the final contract. If RHO passes, I think 3 is likely to be most effective.
Larry Cohen—I’m a 5 bidder. Just get past Blackwood and make them guess.
David Berkowitz—I think you bid an honest 5. I don’t want to push them to a slam I don’t want to save against, but I don’t want to leave Key Card Blackwood or a 5 cue bid for them. My second choice would be 6.
There are experts who think jumping to 6 or even 7 is best. The problem with 6 or higher is that 6 doubled might go down six which is 1400. If you go for -1400, you gain only two IMPs if they can make seven. However, you lose many IMPs if partner has two defensive tricks.
Eddie Kantar—6. Let them guess whether they have a grand slam or not. I don’t want to push them into it by bidding 7. Maybe 4 would work!
As you can see, the only correct bid is the one that works. The majority raised diamonds and hoped for the best. I like bidding 3. It might not accomplish anything but you have a good story if you’re in 3 and take no tricks. The defense to the 3 psychic-bid is that a double of all bids by Responder are takeout doubles of diamonds.
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