Thanks :) I used the default Godot physics. It didn't take much tuning at all, the only thing I tweaked was to increase the angular dampening to prevent too much see-sawing.
Viewing post in Getting Balanced jam comments
Interesting! I couldn't get Godot's default physics engine to work well in my case, possibly because I was trying to keep the scale bowls horizontal. I ended up using the Rapier physics plugin, which had some bugs of its own. Increasing the angular damping on the arm was a good idea - I wish I'd thought of that!