Quote - also you have to have perfect  positioning of your maps when you prepare them for Poser. I place a copy of the "lined map" under my color maps, then zoom in so that I can make a 1 pixel verticle and 1 pixel horizontal cross hair. Then when you copy your map over to your poser map file you reduce opacity so you see the lined map underneath and line up to the same pixel. Its gotta be accurate to 1 pixel.

Photoshop has a handy tool for this a 1 pixel selection line

Why not use the Image>Canvas size... command in PS. Set the origin to a corner, set the units to percent, enter 50% and it should crop exactly; save as, undo and go on to the next segment. You could make an action for this.