I have tested the Copter 3.5 firmware on a Hexacopter, using a frame of the Yuneec Typhoon H, original frame there are the 6 engines and GPS an Ulbox M8 with integrated compass, and the Lipo 4500 mA / h 4S battery.
I replaced the original Flight Controller with integrated ESCs, because they are burned, with Pixhawk PX4 2.4.8, Esc Favorite 20A 2-4S.
I think the replacement operation is successful, the drone flies very well and is very stable.
I attach flight files for a review.
Very nice, thanks for the feedback!