Incubation temperature determines sex, so I'd imagine constant temperature during shipping would be vital, but I don't know at what stage in the egg development.
I've just had a look at the thread that started this discussion (
http://www.faunaclassifieds.com/foru...=651238&page=2 ), and without being ANY sort of tortoise expert, but being a basic biologist, I'd hazard a guess that if they are shipped VERY early after laying, (and at a stable temperature, not sure how you'd control that), before there has been much cell division, you might be OK, apart from the gamble as to whether they were fertile or not. If you ship once the embryo develops further and starts to differentiate into specific tissues and organs, the risk of movement affecting the development would be much greater.
However, I restate my ignorance of the specifics - these are just thoughts.