OK, I’m not creating a separate mastering project, but that’s because I’m using Ozone as a plug on the last slot to do final eq, multi-band compression, loudness (compression/limiting) and dithering. But I think in Cubase you could create another submix for your meters, if you needed more slots. I am convinced that light compression always belongs on the main mix bus, and that’s where I also put amp simulation (so before mastering).