I have a poorly built critchfield that was so poorly built and weak it never hit the water. And so delicate it was very difficult to separate the deck from the hull. I had to sand the fiberglass out of the hull.
I decided to build the boat using balsa core and carbon fiber cloth. I recently posted threads with builders using composite materials and plywood. Both are good options and most builders decide on one or the other. They use the materials they are comfortable with.
Balsa core was the first strengthening material I remember. It was used in my Checkmate boats. The problem I saw thru the years and seen by others was the separation between the fiberglass and the balsa core. The problem was bonding between the balsa and the fiberglass hull. Especially in the hull areas where the hull would flex.
This video offers the solution and explains the problem.
https://www.youtube.com/watch?v=tiS8ArzEA58