If the Ball remains in the bottom of the curved tube.....and never varies....how does one know it is working?
In the scenario you provided....rough air, VMC, and a bit of Turbulence....I would leave the Force Trim engaged, and if in SAS mode hand fly the machine. The autopilot will "dampen" the attitude variations but not return the aircraft to a preselected attitude.
If you use the ATT mode....the aircraft will return or attempt to return to the preselected attitude. You could fly through the autopilot and "assist" it in that task.
Shy of the ball lodging in one corner....I would not be too concerned about it moving about a bit as it is only indicating some Yaw or Roll deviations that result in short term untrimmed flight.
I am an advocate for using the Force Trim all the time....and living with the Calloused Thumb.....set it, click it, tap tap tap....however you must to get the desired result but let the Autopilot fly the machine as much as possible.
Each autopilot system is a bit different in design and function so one has to learn to use them to the best effect.
I also advocate using a bit of cyclic friction to assist in "smoothing" the ride. Sperry Helipilot systems on Bell 212/412's
required the use of a minimum friction setting to reduce cyclic oscillations caused by turbulence or maneuvering.