However, at the start of second stage you are grouped based on whether you have lagged behind or if you have managed to get ahead of other players. The team who is in lead in the end of third stage will be the first ones to land on the island and can search more sectors of it than the ones who get there last.
Is it the amount of sails only that decides this? No other distance or speed calculations needed?

Interested. Reminds me of an old board game.