Must there? Preempts work. Doubles in competition are always
on the penalty-negative continuum and the higher the level, the
closer the ends of the continuum are to each other. What's best
probably depends more on the opponents' preemptive
style and partner's reopening style, rather than any bidding theory.
For instance, with a relatively timid partner you want to play
1m - (2H) - X as negative: spades and a tolerance for S; but if
partner is likely to reopen, there is no need for the negative X,
and a penalty oriented double can serve as a warning which, if
RHO is using EK's style, will likely lead to a plus score.
Fred.