OP, are you looking for a deterministic answer? (if so, ignore this ;) ) Given that responder knows his partner's (limited 1M opener's) hand within a much tighter range, it seems like it would be useful to adopt a mixed bidding strategy: - e.g., with an invitation hand with some likelihood of a misfit, one might pass 30% of the time and bid on 70% of the time ... - e.g., with a weak (0-8 hcp) hand but fit, one might adopt a mixed strategy of preemptive raise/ simple raise/ forcing raise/ psychic bid.