Glad you got the result you wanted as that's what counts, but to master the shadow effects it may help to understand that the shadows are generated from the shadowmaps, which are created from the view from the shadowcams that are parented to the lights. By moving the light, you simply moved the shadowcam, which is what actually changed your shadow. Had you wanted, you could have just moved the shadowcam and left the light alone assuming it was already where you wanted it. The thread mentioned above also explains Poser's often annoying auto-readjustment of the shadowcams which, I would suspect, is the reason you did not see a change the first time you tried it.