After reading other threads that suggest leveling the IMU inside the bird due to DJI's bad installation I decided to give it a try. After receiving 3 quality circular levels as I wanted very accurate levels I preceded to go into my bird. My bird had been drifting left about 6-10 ft when yawning to left and also yawning right it appeared to be drifting but not as bad. Also small winds influencing this somewhat. Anyway I first performed an advanced IMU calibration using a 13"X13" 1/8" thick piece of glass across the motor shafts first as I didn't really want go inside the bird. This brought the drifting inside of 4 ft I would say and I was thinking I would leave well enough alone but I just couldn't. My first crash was because of this yaw drift and my inexperience in flying the thing! Today I went inside the bird and after leveling I have reservations on performing an advanced calibration by leveling the unit inside. As I was waiting on a battery to charge I noticed something maybe no one has noticed and would really like input from you guys. Some have said that DJI has done a poor job at installing the IMU and that due to it not being level is what's causing this yaw drift. I agree that it's caused by the unit not being level, but I think the reason is that the circuit board underneath is swaying in the center due to weight of components. If I calibrate by the IMU unit will this cause the two left motors to increased RPM all the time? I would rather deal with the yaw drift than put more load or stress on two motors, not to mention the bird not flying level. Am I looking at all this wrong?