Yeah this was a big problem I was trying to talk about in another thread about the PLM CPU version. I needed control over what geometry pieces went on which atlases and found no way to do it. Supposedly tags or ID were supposed to be able to be used to tell the lightmapper which UVs went on which atlases, but it doesn't respect the setting. "That's why I was using the "Baked Tag" on these geometry objects via custom lightmap parameters, the documentation says it will force these objects onto the same lightmap and that's not happening. I need to keep the geometry separated for culling purposes so not really a workaround for that. I did pack these separate geometry objects onto one texture atlas in the hopes Unity wouldn't automatically shift and scale them around. I would intuitively think if forced on the same lightmap texture they would maintain their orientation and scale. I guess I'm coming from the workflow with Beast for baked lighting. It maintained the UV structure of imported UV2 coordinates."