I saw in a picture that you were securing them in the foot pockets with a zip tie. Have you found this to be the best way?
With older style foot pockets that don't have a recess for the top screw retention plate, and/or don't have a bottom screw support plate, I prefer a zip tie to secure the carbon blade instead of screws. I can get away with two tiny slots, just enough for the zip tie to pass through the blade.
Carbon blades from different manufacturers vary in quality, some are simply prone to failure. Screw holes on most foot pockets are located near the blade toe angle which is a high stress area. Additionally some foot pocket kits come with ridiculously large diameter screws requiring large holes. Consequently you have a recipe for a blade breaking along the screw hole line, so it is a valid concern.
But using screws does not automatically mean a broken carbon blade. First of course choose reputable carbon blades like Speardiver. Foot pocket mounting kits like Speardiver, OMER Stingray, Cressi Gara Modular and Beuchat use smaller diameter screws. The pressure on the blade is dissipated by the screw support plate which has variable thickness, allowing itself to be positioned to make the screw heads lay flat relative to the carbon blade.
Additionally at Speardiver we never "drill" holes in carbon blades. Instead we use a proprietary method to make the screw holes, it disturbs the integrity of the carbon material significantly less than drilling. Provided these factors are addressed, it's been my experience that done properly a screw installation is safe and durable. Which is why Speardiver offers a two year warranty, including fins that are assembled with screws provided it's done correctly.
Here's a pic of what the installation with a zip tie looks like. The slot is made with a milling bit which means it was ground as opposed to cut. This versus drilling a big screw hole and the fact that it runs perpendicular to the stress put on the blade as it flexes, makes it less likely that a crack will develop from that point.

Safe installation using screws in foot pockets that use a bottom screw support plate and small diameter screws.
