grenv: Of course you are right ! Theory says that if White has beared off all checkers except his last which get hit, then he is a 92% favourite to win the game. It is probably even worse with an open 6-point and 5 checkers on the 1-point. So it is very clear that Black would have had to reject any double by White. I was just imagining the case where Black would have taken the double !
Agreed with alanback too, the double should happen just after that gammon was not possible any more.