My 223LS had the same issue but only on one side. I removed small sections to answer the same questions, only to find that factory construction of that area seamed a little lacking. that area acts like a shelf (only cosmetic) to support the battery('s) and other components. The Battery mounts are just screwed into the fiberglass and are easily pulled out, which lets water infiltrate the plywood and become soft. Simply 1 piece of Plywood sheet on edge to form the vertical wall with another piece of Plywood on a flat. (this area is Not Structural). If you were looking at a sectional view of this area it would look similar to a "L" shape. Several holes cut into the Plywood on the flat so low expansion foam can be poured inside after construction and to add support, then fiberglassed over top. I was lucky enough to remove only the Plywood on a flat, leaving the existing Plywood on edge. After demo, re-fiberglassed over new marine grade plywood with Bidirectional Fiberglass. Sand,paint, New Stainless Steel Diamond Plate (both sides), reinstall components, DONE! She looks Brand New and Better than factory.