I used the 410T in my Shuttles and they seemed to hold the tail just fine. I agree on checking if the gyro is reversed as that would cause the spinning. Once you switch the reverse switch on the gyro you may have to go back to the radio and reswitch the rudder channel. Make sure the tail is going the correct way and make sure the gyro is countering the movement. I recall having to do this on my setup and I'm also using the JR 8103. I replaced my Shuttle Plus 410T with the 500T and that was a far better upgrade.

I belive I ran my 410T gyro gain around 60% or so with a JR 810G sport tail servo. This setup served me well for over a year and a half worth of flying.