My Cal T-4 has wet and rotted plywood in the ceiling of the cabin. I cut an inspection hole through the thin fiberglass covering the bottom side of the ceiling and found the plywood comes out in shreds. I pulled enough away to expose the fiberglass of the top deck. Can the plywood be replaced from inside the cabin or does the top deck need to be removed? I'm pretty competent with home repairs but I'm new to boat repair. Any advice on the best way to proceed with this repair would be appreciated.