Statto, on 2012-February-22, 16:25, said:
I've not played Crunched Cappelletti etc, but I'm wondering whether the effectiveness of these systems is based on the assumption that opps interference will be negligible.
Depends on which version. Most of the time, however, any call by Responder through 3
♦ (and probably 3
♠) causes no realy problems for us, and higher intervention probably means that it is their hand anyway.
In other versions, though, two-under is actually less intervention-susceptible.
Consider a simple example, playing against Weak 1NT. Your LHO opens 1NT. Playing simple Landy, partner bids 2
♣ for both majors, 2
♥ for hearts, or 2
♠ for spades, and your RHO next bids 3
♦. You are preempted by the interference and have no idea what partner's strength is.
Playing the simplest version (suitable and perhaps idea for weak nt overcalls), however, partner will have instead bid:
2
♣ for weak with one or both majors
2
♦ for both majors, intermediate
2
♥ for hearts intermediate
or
2
♠ for spades intermediate
In that structure, the interference is less costly than with other approaches where Overcaller has a huge range. For that matter, if Responder passes (no interference at all), you are better positioned as Advancer to decide whether 2M is enough or to move forward into the three-level if you know partner's general strength.
Conversely, because you have both a weak and a strong way to show one major, or both majors, you can have a wider "range," not passing weak but playable hands (and hence less susceptible to intervention) and not having to double with some high-end intermediates (also a problem if intervention occurs after the double).
Some of the more complicated versions have similar range protections, like a Crunched Capp with a "power 2
♦."
In Mid-Chart, you can even show range for minor overcalls (e.g., bid 2NT for both, 3
♣, or 3
♦ with values, but 2
♠ for one-or-both-minors weak).
So, if strength and interference-protection is your goal, that is also answered.
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