Sportfish bow explodes; too much flare?

Also much larger length for length. People say a Viking 60 is the same as an Azimut 60 when they compare.
But the reality the Viking 60 has 64 of LOA without a bathing platfrom, the Azimut will be 60 with pulpit and BP, and the Viking will have a 20 to 35% of more beam.
Result an Azimut 60 will need two 1000hp engines and will do 35 knots, and the Viking will neeed to 1500hp to do the same.
Yes sportfish are constructed heavier, stronger and run very good, no doubt about that but it is good to compare apples to apples.

As for the above Carlo Riva remark, he was influenced by Chris Craft but in reality he started more or less with them, his family boating business is even older.
And in the Lake area of Italy, there is other pioneers as Baglietto, and the Abbate family.
His Chris Craft influence had nothing to do on the designs, but was more about how to make his wooden runabouts produced in a commercial sense, it is there that he copied Chris Craft the most.
There was a two dozen builders doing wooden runabouts in Italy alone.
As for modified hulls, I mean those are nothing new. Be careful at the entry because most traditional hull shape used convex hull, which is why a hull like this would dive to much in a following sea.
As Sonny Levi once explained to Don Aronow you have to go always with concave above 40 mph.
I think it was a Cigarette 38 which stuffed in Italy and basically finished in two parts because of its convex hull shape.
Convex works well in head seas, though buoyancy needs to be given a lot of importance, but concave is the way to go above a certain speed and in following sea is king.

Some History of the famous Riva:

"In November 1962 the myth was born: it was named Aquarama. Since its presentation, at the third Milan International Boat Show, the Aquarama became the symbol of Riva par excellence, almost "a brand within the brand”. The prototype was the mythical Lipicar no. 1, the evolution of the Tritone. 8.02 meters in length, 2.62 meters wide, capable of sleeping up to eight people, two berths at the bow, two 185 hp Chris-Craft petrol engines, a speed of 73 km/h. "

These were the next generation of his Tritone line which was done in the 50's, those also powered by Chris-Craft engines.
But note the famous Christ-Craft wooden runabouts were built as early as 1927. It would be hard for any boat builder not to be influenced in part by them. Interesting to note that both Chris-Craft and Sea Ray were companies located and founded near Detroit that went on to become big Industry names from the same region, the manufacturing capability in that area was just unbelievable.

My favorite Carlo Riva story was his relentless search for some engine related failures that were being built by Chrysler in the US and causing him warranty headaches. He personally went to the Chrysler engine factory and went down to the production line and witnessed the casting of the engine blocks were they had a manual process of using a sledge hammer to free the casting and this was causing a small fracture that was his warranty problem. He took the time to find the root cause when nobody else could, now that is a passionate and driven boatbuilder!

As far as the Concave/Convex hull shape something does not seem right in your post. Here is a link to a Michael Peter's article on the topic with a reference to Sonny Levi as well, and the Concave sections disperse the load while the Convex sections create higher impacts:

https://www.proboat.com/wp-content/uploads/2011/04/hispeedpowerboats126low.pdf

If anything, those early Cigarette's had straight sections similar to their Formula 23 and Magnum origins.

We do not have to have arguments on the topic my friend but open discussions usually arrive closer to the truth than not.

The forward Bulkhead did its job correctly as the bow fell into the trough of a 3m sea, which means the "hole" left in that trough could have been up to 5m. Ultimately, the boat left on its own power and went to the Boat Yard and will play another day with that regional Carolina flare reinforced for a second life. They flare is a local design attribute for a good reason and while some are more extreme than others, it comes with the territory. The Buddy Davis boats were the first major boat builder to produce what was once only available to a custom project. It is part of Americana and here is a nice book on the topic:

https://www.amazon.com/Carolina-Flare-Boatbuilding-Sportfishing-Heritage/dp/B0026OW6F0

As far as cars go, the muscle car era was a fantastic time of large V8's with high horsepower in what were at the time unrefined production cars. That is the influence we experienced in the US.

To compare Ferrari's to a US production builder is a usual but wayward response. Building 50 specialty cars when Ford is building 50 an hour is a far different animal meant to be enjoyed by the masses, not the elite. And when they wanted to , we all know what they really could do with a Ford GT and the history behind that program. But those are discussions meant for relaxing ocean view bars with drinks to go around for all

Let’s keep the discussion of convex/concave from the chine and below.

Topsides (above the chine) introduces a complete new language with old fashioned Naval Architecture terms terms like flim or flam to describe bow flare.