I'm trying to create a new hair object by opening it in UV Mapper, exporting the new .obj file and then inporting that into Poser. It imports as a huge object and trying to scale it back down and behave as a hair object is really tough - am I missing something? Thanks

You did not say, but if you created the object in a modeler, then this is where the size comes from. I do not think UVMapper takes size into account for mapping. I would not be surprised if it had a scaling function, it does so much, but try rescaling the object in the modeler before you save it. If you have a part of a Poser figure in the modeler when you shape the model this should keep the size comparable if it is RDS or Carrara you are using. I think Max has size problems with the tiny Poser figures, other modeler may as well.