I am not a wizard in the weldments aspects of SolidWorks, but I have a couple general questions?  Is it required to use the 3D sketch to create the "wireframe" of a weldment feature?  I have a product that I would like to produce on the top plane because all of the various standard structural members would align on that plane.  Also, I have some sheet metal parts that need to be added to the weldment assembly, multibody part.  What are the best practice methods of accomplishing this?