Interesting... and nice work there, Kurt.

338 has no balsa anywhere in the cockpit or the cockpit cabin side (which is hollow in that the liner has no backing).

Plywood strips were used to increase stiffness
under the deck
under the seats and lids
under the cockpit floor.
These pieces were added to the molding when it was upside down being made in the factory. Each strip is isolated and molded in with wads of mat.
Really surprised you have found such extensive deterioration. Wonder if a DFO was is there at some time. Doubt that Pearson encapsulated sheet or areas of plywood. Just an observation.