I have not seen pass after opponent's XX as being played for penalty. In my experience the typical interpretation in ACBL-land would be a lack of preference. A second consideration of this situation is the need for a way to expose psychic XX's. We do that with an initial pass and then a free bid: (1m)-X-(XX)-P; (P)-1M-(P)-any which is natural and shows good values. (If you live in a psyche-free world, this is not needed.) Eric S.