Lets say that balsa is still not a bad structural material. I have been talking with one cat builder who is currently using Nadi-core, and they are probably going to switch back either to Baltek Balsa or Airex Core materials. In our conversation, I pointed out that many of the softer foam cores, do not do well in compression. I have seen a number of boats with foam core, and where they have hit a piling or dock, there has been a "dimple" of damage to the outer glass and compression of the foam core. Balsa end grain tends to resist this type of compression injury better than foams. Part of the problem is that builders put less glass on a pannel (ie hull side) when they use a core material. This makes the core more susceptable to damage. One of the positive features of the C Dory is the thick outer skin over the balsa core.
For one, I would rather that the builders stay with balsa, and do proper sealing of the core material, where-ever fittings or fasteners go through it.