We just built a new American Tug 395 that we took delivery
of last year. Although the hull on ours is solid laminate, they in fact use balsa coring in a couple of spots in the deck
. When I learned of this I too was distressed. After a long discussion on the virtues of Balsa coring and the strength it can add if used properly, they did offer to build our deck
with other coring materials if we chose. In the end we elected to go with the Balsa.
I believe a lot depends on the manufacturer and the construction of the boat
I’d find a good surveyor
familiar with the Swift line to speak to on the subject...