Okay .. . update: I tried using Split Vertices on a version of the OBJ that I exported from Poser with Weld Identical Vertices checked. That ended up spliting every single polygon edge in the model, so it shows up in Poser looking faceted. Another thing exporting from Poser with Weld Identical Vertices did was weld the verts across this problematic seam--so they are in fact identical, or at least Poser thinks they are when exporting. Next I tried subdividing the heck out of the area where this is happening, thinking that perhaps there was some angle threshold for the CR2 to actually weld the edges like any other body part seam. Even with like a gabillion polys making the transition very smooth I get the same problem. I's Confused . . . :(