Collecting some data to illustrate some more advanced coffee roasting concepts and I just did an 8 minute roast to an end temperature of 502F (about 40F hotter than my darkest production roast). 22.4% mass loss, gourmet scale 20.5. I don't recommend replicating that at home (if you want it that dark, it's probably better to spend more time and get there at a lower temperature).