Nice video.
The only way to avoid a carbon fin from breaking in Pathos footpockets is to make it significantly stiffer, to the point where the flex is not to my taste. I prefer a softer fin, it tires my legs much less and gives me the same propulsion, also allowing a better breath hold. Having watched the video, I can tell you starting at 1:27 that is a stiff fin.
This may be the reason he doesnt have a soft fin yet. He only has med and stiff. The med are stiffer than my leaderfin med. but not as stiff as the GFT softs i tried.