This comes from further back on this thread. I knew about these videos but I could not find them at the time and they are interesting in what regards to show the solidity of a narrow well built keel in what regards its attachment to the hull.
The boat is a Sigma 400, a light performance production cruiser from the 90's and still today a light and competitive boat (7500kg) by today's standards, a boat well ahead of its time. That boat was still in fact a local champion and a race winner, it has a big draft (2.29m) ballasted keel. It is a design from Rob Humphries the same designer of the Elan 400. We can see that not only its keel stood up but even the more fragile ruder is still in one piece. Off course the boat needs probably to be repaired but this was just not a sigle hit but a massive pounding.
Great story here
Sigma 400 Boats for Sale