I am not sure I understand the problem with the shadow volume rotating with camera. Are you making your own shadow volume, or are you somehow getting your slices to cast shadows using the regular translucency as the sheets? If so I would kind of expect that since you are slicing the volume based on viewing angle which will change how the slices align from the lights perspective. Ie if your light angle is at 90 degrees to the view angle you may get very thin or disappearing shadows since they will be invisibly thin from that view. Half angle slicing also addresses this. You could probably do half angle slicing just as an angular setting to fix that without actually tackling the more complex light accumulation method that it usually refers to.