Control-clicking on the CHANNEL wil select all the white too, and the half-white half! You use the channel as an alpha channel. This might help if you have too much of a white halo. If it cuts away too much you can multiply your LAYER with a copy of itself. Just keep this in mind when you bounce into problems. I do not think you will, because if you set your Poser template layer to 'multiply' halos are nowhere to be seen.