title_body: How to tune a Deadcat Quadcopter with 10 inch props and asymmetrical mass distribution along the roll axis with a low power to weight ratio?
upvoted_answer: The discovery frame uses the old DJI plastic arms and the arms are not very stiff. So you get a lot of flex in the arms. This leads to two major problems: vibrations and the quad has a relative long delay until force of one motor really starts to rotate the quad. This problem gets amplified if you are using out of balance motors or very felxible propellers. This would explain the unstable flight you are describing.
  I'm afraid that this is a &quot;hardware problem&quot; and not a &quot;software problem&quot; that you can fix with some PID settings. Modern flight controller firmware is built with certain assumptions about the used frames/escs/motors. A 10 inch prop on a 810KV motor with 3S and a plastic frame isn't a target platform for betaflight or any other race/freestyle oriented FC firmware.
  What are your options? Make the frame as rigid as possible and try to dampen the FC so you get rid of the vibrations (e.g. put double sided tape under it). I don't know what FC you are using but try to get some blackbox logs to see the frequency range of the vibrations and try to add more filtering to clean up the signal for the FC. After that you can start to tune the PIDs and maybe get a flyable quad. You can tune the quad without any flips and rolls because with a low power/weight ratio the quad will probably crash in the process. So just tune the quad for regular forward flight.