On the latter, if you disable auto-scaling Carrara will indeed keep the object at the same scale; you can export from Poser and re-import after working on it in Carrara. Unfortunately the Carrara tools are not very good at that scale, so most people will scale up by 500 or so, do the work, rescale at 1/500 and export again. But there is an oddity. I have not tracked down whether it is in the scaling process itself, but re-importing to Poser at that point seems to have displaced my objects a small amount in space. Easily corrected in Poser, but annoying. (Obviously, you also want to disable auto-position on the Carrara end, and uncheck everything on the Poser import. The Poser export settings depend on what it is you are doing. For the most part I uncheck everything but "keep existing groups." And on the Carrara end I import as Vertex Object, one polymesh, one object.)