I used edge crease at 1 and it's on a subsurfed mesh. I extruded inward and got the ugly blotches I see here. I've seen these on some models that are textured and materialed and render great without it showing up. I wonder if some texture or such covers these.
You can see them on the edges of the hull outside the extrusion.
In many cases I fix these by using a loop cut to slide an edge up to the edge of the extrusion, at about .9 closeness. If I do it here it dfistorets the shape of the hull and gives it sharp edges and points on what I want to be a damn smooth, curved hull.