In my next game I will disable the culture flip possibility. It never works for me, not even when i'm really strong in culture. I think it's also unbalanced and unrealistic, like when an AI gets beaten down to only a couple of cities but still got the same culture value. It should dimish over time when an AI's power is weakend. When a city flips, I think war should be declared automatically. What would happen in the real world if a city in country A "decides" to join it's neighbour country B? Just because the TV-shows and theatres are better in that country. Do you play your civ games with the culture flipping possibility?