Rotary jig , STL importer unwrap is incomplete

[Tatay44]

I do most of my art in 3d and stl is the most common that i use from obj. My issue with the stl importer is that when it unwraps a figure it doesn't work with arms or legs or any object thats away from the main body it always fills it in instead of carving it out. Anybody that knows a work around it would be appreciated since the object of having a cnc is to have it carve most of the figure so that only details and sanding are necessary.