Xnr,
The way you fly is not governed by the design FAR 29, have a ball with the trim button! You can use the techniques that suit you best when you fly (unless otherwise restricted by operational FAR), but when we certify to the requirements for the design, we must show that a means to provide force vs airspeed exists. On an S-76, I myself would not turn the trim off with the panel switch in IFR, because I then disable the Attitude stability and leave only SAS, which is less suitable.
GLSNightpilot points out a problem with flying against trim that I failed to mention previously. In most aircraft when you push the stick against trim, the inner loop actuators fight you with some of their authority (since the stability system sees this maneuver as an outside disturbence). In the S76 we limit the attitude authority of the actuators to half their travel, thus saving the other half for rate damping. Biased actuators in a staedy maneuver then reduces stability authority and makes it somewhat more prone to running out of authority in turbulence. In other words, if you ride against trim you can get closer to the point that turbulence can upset the aircraft. This probability is much more real than the possibility of disorientation causing you to need to let go and hope the aircraft rights itself and saves you against yourself.
Regarding the beeper hat authority, the S76 beeper is timed out so that the failure of that switch does not cause the AFCS to run away in a hard over. The upset at high speed would be too large, and the loss of the attitude hold would be guaranteed, so we put the beeper thru a timer to limit the runaway.
heedm points out ANOTHER reason why trusting the trim to save you when you give up and let go of the stick is not a swell idea. If the trim has a failure that causes it to run away (this can be a switch failure in the cyclic) then the stick center is wrong. If the pilot gets disoriented (as heedm did ) and then trusts the trim to get himout, his goose is cooked. I am not sure why heedm deduced from his experience with this failure that letting go of the stick was a good idea.
Nick