I've done a few searches on the board and I can't decide if putting the phantom on a 'perfectly level' surface is required when doing the advanced calibration. Even of it's on a perfectly level surface, the landing gear has foam pads on it that may make the actual internals out of level. If the surface that the phantom is sittng on is level by checking with a spirit level in 3 or 4 places, surely that has to be enough. If anyone has any facts or opinions to share, I'd be curious to hear them. Thx.