Helo Everyone,
Another thought is that your 4 in 1 is heating up also. I did a mod to my rx case and it was like night and day. If you get really good at keeping it in the air you can take the next step as I have and remove the case all together and just double stick the circuit board to the frame.
http://www.dacaur.com/bladecxhelp.html#gyro
Since this mod I have had no issues with tail drift, other than the slight movement through the decrease in battery power
It is also imparitive that you have the cx level when plugging in the battery. Do not touch it again until the green light goes solid.
Mark
Keep it in the air, not in the garbage can!