Fsbus servo board

Hi,Has anyone used this for Elevator Trim indication or Flap position.One observation is that when you assign a FS function to a Servoyou cant delete it like you could say with a Analogue input.Not really an issue.The second which is more important is that if i try and set it up for Elevator trim indication it seems to work ok when you move the test slider.However when you are if Fs9 the indicator sems erratic and doesnt seem to track the graphic indicator in Fs very well.I have tried to do the Flap indication,but this doesnt respond at all in fs.using the test sliders,the servo operates.The servo i am using is an unmarked brand bought from a local electronics shop and travels 90 degrees.Any help would be appreciated.Les