EV -0,5 on every Gopro model I've owned (4 generations so far) or the highlights will burn. I run 2.7k30 iso100 most of the time, just the ND filter changes based on how much light is available and I use as little filter as possible because I don't like the motion mush. If it's night and streetlights, I just push the footage in the post because it's still better than the higher ISOs of the Gopro. ND filter and hypersmooth rarely agree, so you kinda have to do the stabilization in the post. I don't do it myself because your sticks are supposed to smooth the footage, but there's a FREE software option for stabilization, which is rather popular with the freestyle pilots called GYROFLOW. You can use either gopro gyro data or FC gyro data through the blackbox to stabilize the footage and the results can be as good if not even better than what the Gopro solution offers. It can, however, be rather fiddly of a process, too.