There is one type of hand that does not fit into the Chilli opening structure – a minor two-suited 5431 not strong enough for 1
. We keep our opening 2NT true by insisting on at least five-five in the minors, and 1NT may be 5422 but not 5431. In third hand, we can open two of the longer minor, but in first or second hand that option is not available.
So we recommend pass. This is not that arcane: the chances of the auction being passed out when you hold this shape are small, and if it is, your hands are probably a misfit and zero may be good score.
And we believe the benefit of keeping openings disciplined far outweighs any possible loss on an individual hand.