[maitaman]

The idea of replating is mostly a change in nutrient levels and to stop the overcrowding. It can be done when the protocorms are no larger than pinheads (so now to figure which size pinhead!). I've replated when they were no more than small green dots, but have better results when they are a bit larger. It can be done anytime after the protocorms form, but is better done before roots and leaves begin to develop. Allow room for the plant leaves to reach the top of the flask/bottle/whatever. A friend uses baby food jars and puts 5-7 per jar. A larger Erlen-myer flask can handle about a hundred plants comfortably, but roots become entangled so care must be used in separating them for compotting.
You can leave them in the mother flask until compot size if you don't plant too many. It will be slower, but works.