The latest GoPro uses a different plug/socket from the micro USB that is standard elsewhere. I've a Hero5 and it's now USB-C. don't try and force a micro USB in to it, you'll damage it.
Bought an 'action' camera that has a microphone built in, for £16. I took it apart and put a 3.5 mm socket in the case. I removed the microphone from the board and wired the 3.5 mm socket in its place. I then modified a headset splitter lead with a 3.5mm jack and inserted 2 suitable resistors inside one of the 1/4 inch sockets. This provides excellent audio from the aircraft audio system. Don't try and feed the audio in directly, you'll overload the input circuitry. Whilst the video quality is what you'd expect for £16, it was a good project anyone with a small soldering iron can perform at a lot less cost than the GoPro lead! I use this secondary video for another in-cockpit view and put it in a small pane in the main GoPro video, which is shot centrally from behind the 2 front seats.
One problem with suction mounts I've found is getting them to stay on curved Perspex surfaces.
Avoid any trailing leads anywhere that might interfere with an emergency evacuation (one of my hobby horses...)
TOO