Solid surface detection/generation seems to have problems with certain objects. For example, I sliced
this motor mount with 4 solid surfaces, 4 perimeters, 0.25 layers and 1.8 w/t and the top end had only 1 or 2 solid surfaces on top of the sparse infill instead of 4.
This object is a bit unusual in that it has been generated in ImplicitCAD which produces meshes with a lots of triangles, but it prints otherwise just fine and has been checked with netfabb.
