i personally recommend using rafts for only for crossing rivers or scouting the coast, as often the central starting island is on most seeds i've seen a circular archipelago. raising the land to make a bridge prevents this exploration possibility.

The reason being is that later in the game it becomes useful to be able to sail into the middle of these circular set of islands as i've often found myself returning there to find deposits of copper i didn't bother to look for before i left.