i'm also having exactly the same problem with my sl420,no matter what i tried,i couldn't get the gyro trim feature to work,it kept on pirrouetting every time i switched it to normal mode.the only way i got round it was to use a flight mode switch for gyro switching{sanwa rd6000 sport radio}and then use the radio's trim memory feature to set a different rudder trim every time you flick into normal mode via the flight mode switch.the heli will then stay in perfect trim in both gyro modes because the trim changes as you change modes.i'm not sure if you would be able to do this with other radio's though.if there is any body out there that knows the correct way to deal with this problem then please let me know!