Mix together the fish sauce, lime juice, and sugar. (Stevia is a decent replacement.) Stir until sugar is fully dissolved. Set aside.
Pell the pomelo and separate into segments. Remove any peel. Place the fruit in a bowl.
When ready to serve, pour off any of the juice (I reserve for dressings). Add the coconut, peanuts, shallots, mint, and chiles to the fruit.Pour the dressing over and mix well. Add more lime, salt, or sugar to taste.