Hey, I think I did it! This was the mesh for Rex's Mertail, but I managed to get it to unwrap and everything in Blender. For the heck of it I still ran it through UVMapper, but that just produced the same map Blender did. As far as I can tell, there's no distortion at all. There does seem to be a slightly imperfect seam along the back of the tailfin but I can easily live with that!