Matt, I think most designs today have flotation to keep both the platform and crew afloat with swamped hulls. I dont think the F-18's would do any better than the HT's if you hit something substantial with the daggerboards at speed.

Saying that the F-18's have better construction than the F-18HT's would be a misunderstanding in my opinion. The HT's went for low weight and carbon. The F-18s for easy mass-production and affordability. None of them was designed/constructed to hit something with their daggerboards at speed.

If you sail in areas with lots of shallows, what you need is either a boardless design like what you sailed, or a design with centerboards that kick up, like the Tornado. What you loose with those alternatives compared to daggerboards are top-speed and pointing.