In the absence of any advice, I adjusted the angle gauge so that the center of gravity was always trying to close the choke. This isn’t really how most of the instruction graphics I found indicate, but as I said, allowing the air flap to flip over with the tool weight results in not moving the flap if the tool isn’t in place.
I was expecting failure with the carb on the vehicle, but it actually works okay so far.
So if the way I was using the tool is wrong it doesn’t seem to result in any issues.