First test of the fixture is a partial success. Nothing broke. No-one was injured. The joints don’t mate. I left the -0.125 mm allowance that has worked well in the past. I’m thinking I didn’t rotate or reflect the joint design correctly. Since this is my first asymmetrical joint, that’s probably the reason. The other good news is that the angle is exactly correct, within measurement error.
Man, it sure was nerve-wracking though. I don’t like long bits or deep cuts. I reduced the feed rate to 40 IPM with a 6 mm pass depth, so it was fine. But still, had the heart rate elevated.