I have been using DesignSpark for about 10 years. I feel confident in designing parts for 3D printing model yachts. I recently updated both DesignSpark and Cura for slicing. I had trouble with DS in that for a few days I could not get a design into an STL file . I reinstalled and finally got back to designing parts..For the past week all my models are hollow and useless. Just once I found an option of converting the model to a solid( I think thats what it said )since then I cannot find it.I tried fill and that does not work the way I need it.I even pulled a simple cube and that is hollow. Selecting Solid in the structure column does not help.