I actually did fly through in RL (!! nerve racking!!), but for the video I cut it because the shadowed parts of the wall pixelated in the footage (was at 2.7k 60fps on the GoPro) when I went under... so I cut that clip just before the pixelation set in... anyone else have this issue with Hero 4+ footage? I think my error was that although I was set to shoot flat, the 'GoPro colors' was accidentally left on. Perhaps that's what did it?
Anyway thanks for checking it out better and better every time thanks to the wicked info found on this forum!