I'm rebuilding my cockpit floor because it's disbonding due to moisture in the balsa core on my Irwin 28. I have the same issue as you do with access. I'm fabricating a 20*24 access hatch into the cockpit floor out of solid fiberglass and aluminum while the remainder of the deck will receive a foam core 
I'll have pics on here eventually of the project once I get to the floor fabrication
I'll have pics on here eventually of the project once I get to the floor fabrication
