That is true, with a HH gyro, you don't want any regular trim. And 34 seems fairly high on subtrim as well. The only use for subtrim on rudder is to get the servo arm at 90deg....what arm/servo are you using? I have the S9650 and round arm and didn't need any subtrim.

Also, when you say the tail drifts right/left....is this in HH mode? The tail should not drift at all when in HH mode.

Give some more info: gyro, servo, heli.

If you haven't watched them yet, watch the Finless Bob video's over at helifreak....there is one on setting up the gy-401 with a S9650....there a a lot of good ones there.

Skarn