no sorry, David can only close the mesh, can't create a thickness of the walls.
This is a tool usefull only for 3D printing, and David don't have this features.
There are some ways to creat walls, with many different software. If you can have access to Materialise Magics, it have a function to create thickness and specify the amount in mm or inches. A freeware (but more complicated) way is, with other 3D editing software, to duplicate the mesh, flip the normals and reduce its size. It the object have a simple shape, it can work, but if have articulated parts and undercuts, this couldn't be work. So you need a "shell" or "offset" tool of the 3D software. By this way you cna create a inner shell (eg.: 3D Studio Max have this modifier) or create an offeset of the surface. If you work with ZBrush, you can duplicate the mesh, push it in side and simplify and decimate it. Invert the normals and save all as a single mesh.
Remember also to create little holes in the voulme, if you aim to use liquid resin printers.