Try turning the AVCS off and run the gain about 50%, your ship is probably nose heavy adjust the batt to balance the heli on the flybar. if you cant dont worry just move the trims so it stays still and then reset the swash plate to where the trims are then recenter the trims. So the swash plate is in the position of where the trims were moved to before you put the trims at center.Does that make sense??? i just re read it and i dont know???LOL. It will need little things like that to make it as steady as it can be,nothing is wrong that is how you do it.The tail rotor blows air to the right so the ship will drift left you have to adjust for that by putting a little right cyclic in the swash plate adjustment.
I hope that helps and if you need anything else just ask.