As far as scaling new models to the Poser workspace... I have found it simplest to just build the model in Carrara, import to Poser with "send to floor," "center," and "percent of figure size" checked. Then using either a figure for eyeball reference, or one of the various rulers kind people have made, I scale it, align it the way I want it in the Poser universe, etc. Export from Poser again, marking the file as "Poser Scaled." (Again, the usual setting is all unchecked with exception of "keep existing groups.") In the case of, say, conforming clothing, I have found it simple enough to open and zero the figure I am conforming to within Poser, import the new mesh as above, switch to isometric camera and wireframe view, and scale and shift the object by hand until I have the best fit possible. Then export, again as above. After that I can bone the new garment and otherwise deal with it normally. (Same goes for smart props).