Someone better call Boeing and tell them the 787 carbon wings aren't going to work if they flex with turbulence! Joking aside, I understand your point but I'm not super worried about it. Kuiu is working with an actual carbon fiber design house. If they did it themselves from kits I'd be worried. CF has been around long enough that a good shop can design parts to stay in the elastic regime meaning it's flexing but not undergoing any permanent changes. It's possible they didn't design it correctly, but with the testing videos and reviews it looks to be fine. Part of the CF process is trial and error which is why they've gone through so many design changes. That's part of the growing pains of that technology.
This sounds like the issue. Although the guys below talking about size may be right too. I'm near the end of adjustment. I'm down 50lbs this year and have another 25 to go. When I get there I'll probably bottom it out. In the picture the plastic bar twists like this every time I try to get any tighter. It's about max tightness in the picture, but I'd like it just a little more snug. The kuiu system is absolutely effortless to get a crushing tension. I'm not sure if it's the hardware or angles, but it works so well. I'll give kifaru a call and see what they recommend.
Edit: The picture didn't work before