Tell you what: send us a track of you trying to handle that trim. I'm sure we'll be more helpful that way, as we'll see what you could do better ;)
On a sidenote, to avoid confusion, FD mode is (yet another) autopilot mode in the KA. It stands for "Flight Director". This mode uses the currently active AP channels to smooth your control inputs and make the helo much easier to fly. But it overrides the AP channels 20% authority over the controls, which means that if you re-center the stick, the helo won't try and get back on the trimmed attitude.
This is a great way to free-fly and chill out, but also to use your rockets, actually.