I obviously have to adjust the trim as the battery drains, which is one reason why I am going to a belt system in the future. But I have also noticed that diffrent batteries require diffrent trim settings on the tail. Unfortantly I don't have much of a suggestion for you on this if your using the stock transmiter. What I do is I have several profiles on my transmiter for my cpp and I pick the profile that fits the battery. That way I don't have to retrim to each battery it is already pretty much set.

One other thing to note is how much tail power you need will vary based on your pitch too. So what may work at a hover about a foot of the ground (say 60 to 70% throttle/pitch)...will not work for a higher pitch or throttle setting. This extra pitch creates more drag and thus has a greater torque effect. So as you increase pitch you will need more right side trim.

If your tail is twitching back and fourth then my guess is your gyro gain is set too high. Basicly your gyro is over-correcting and this is what is causing this twitch. If it not going back and foruth (also described as the tail wagging) then something else may be the problem. But keep in mind these POS stock gyro's are not very good at holding the tail as it is....that is why I plan to get a heading hold gyro soon (maybe 2 weeks when I have more funds).