I am using SbuilderX 3.15 with Prepar3d 4.5 although I am sure this issue applies to older versions and other tools. It appears flatten polygons (which includes water terrain) flatten an area outside the area of the polygon. This makes having small steep sided islands impossible, the water flatten flattens the island. Is there some form of workaround that anyone has come up with? The best think I came up with is creating water terrain with no flatten and the judiciously using bare flattens a distance from the shore, but this has its limitations since the bare flattens appear to do a rectangle which still somewhat affects the island if I have 0 sea level water right up to the shore.