Probably not best to do at flip then I'd say.Most plants will bust through the bag in about 10 days. Just be sure to water it in good. You'll want to be sure to get a good amount of water where the bag is and outside it to force the roots to go looking for water. I've had 1 or 2 plants over the years take a little longer to get through. You can tell if they start to wilt within a few days that the roots aren't busting through. If all goes well you won't need to water for about 10-14 days after transplant.