Losing that much I would think you could SEE it. I would also try letting it set a bit, while warm, and then pulling the plugs and see if they are wet. Does it miss any on start up? Also look at the tailpipe for excessive moisture, and see if you can smell it back there.
I've sniffed the exhaust already and didn't think it was smelling different. I have filled up the overfill tank over a week ago and it has not lost any coolant so far...
