That's pretty close. I duplicate with symmetry in the Assembly room, then go back to the vertex room and pull the preview window open as far as I can. Then I can work on a half-object while having a preview of the whole. When I'm done, I duplicate and weld in the vertex room and throw away the other duplicate. I just started doing this on a recent project and I like how it works very much. "Detach polygons" is used to make a seperate, non-contiguous mesh out of a selection. Say, if you modeled a can, detached the "lid" polys, then detailed them to make a seperate lid for a now open can. I stumbled upon this command a long time ago as a way to clean up the strays that Carrara still seems to create from time to time. I am convinvinced that the majority of the vertex room problems can be traced to Carrara trying to influence some random vertex somewhere else, or a phantom vertex you deleted but it still remembers. "Detach Polygons" cleans up the selection to just what you, well, selected.