I wouldn't lump the F18 with that label. I believe some F16s (as well as other cats) suffering from structural problems also. Mainly during the early stages of development of a new boat or it is a manufacture error, not common to the class and is rectified through dealer warranty. I could pull some pics of some F16 failures if you like, but that would benefit no one.

As for stiffness, I see your point. Too stiff can cause failure in other areas, however I do not believe OTB cats are even close to that. The Viper is very stiff. It could be made stiffer again and much lighter but that would come at a cost. To some, they would not be willing to explore those limits. To others, if the prize was great enough, then they will go to extraordinary (including financial) lengths to achieve their goals.

The other current F16s are close to minimum weight but could do a lot more work in the platform stiffness department. If the higher volume hulls are more beneficial, then they could do further work there...... however it would come at a great cost.

Raising the minimum weight will not solve this problem (at least alone). The reduced use of exotics is the only way to keep the cost in check. The class has not seen this yet because it is still a very small class produce predominantly by small localised manufactures and are nearly invisible on the sailing scene despite being perhaps the most visible on the internet. If the class really starts to make a strong presence on the water and attract much larger fleet numbers, increase competition, then this will change.