We have created a huge Agri drone(14L capacity) using Pixhawk 1, the copter take off and landing is pretty good in stabilized mode . However I have not done PID tuning, the copter is tuned to default PIDS.
What is the best way to tune the PIDs , as I do not wish to go with auto tune procedure keeping in view of battery support , I am not sure copter can hold for 5 mins to complete the auto tune procedure.
FWIW from our experience (we only have a 15kg MAUW Hex) is autotune is not the best solution for an agri-drone. Just think of the differences 14kg will make to your tuning from take off to landing. We just manually tuned to the best average. We err on a little less ‘locked in’ machine when fully loaded - we allow it to decelerate slowly and reduce the lock when hovering to keep the loads off the airframe.