I presume you mean GSA28, Garmin's autopilot servo. The GA28 appears to be a marine GPS antenna...
Just to clarify, are we talking about flaperon trim via the GSA28 servo, or elevator trim via the Kitfox-supplied DC linear actuator?
If you mean elevator trim, then how/why is the GSA28 servo involved?
Set me straight on those questions and I'm sure we can get your trim sorted out!