I travel many times with my dogs 12-24 hours(by train), just for shows, exams and holiday and I never have any problems with stress, because my dogs are use to traveling ...all I want to say by this, all(most) dogs can be trained for everything, if the owner want it strong enough
...another option could be to pay the owner of the stud dog to travel as I think stress would not have any big effect on the stud dogs performance and it that way you would eleminate the risks by stressing the female in such a way that she will not stay pregnant.
Just some thoughts !
Rolf