As Bergen once said... stopppers are for bottles. So many ways for 3N to win... Either we have a stopper, Or we don't have a stopper and they don't lead it, Or we don't have a stopper and it splits 4-4, Or we don't have a stopper and it goes -1 but 5m is down at least 1 also (not uncommon when you have 2 losers in one suit), etc