I tried both FreeCAD and SolveSpace [1] a couple of years ago on Linux, to design a custom computer desk that had to fit into a fixed space, so a parametric CAD with constraints was useful. For that purpose SolveSpace was a lot more stable (IIRC it only ever crashed once, whereas FreeCAD crashed a lot more often). YMMV those bugs may already be fixed by now, but if you are having trouble with it I'd definitely recommend trying Solvespace, and in either case save often! [1] http://solvespace.com/index.pl