Fishman, Did this job last year and found different thicknesses of balsa depending on location. Cockpit floor is usually 3/4" as well as most areas that get walked on. The idea behind balsa is that the vertical end grain does not take in water
and spread it horizontally due to the grain direction. If properly saturated with resin, if and when it gets wet, the water
has a hard time moving. Plywood
, as well as being heavy where you don't want it, once wet will quickly move water all over the place. I also found that any idea about reusing pieces of deck
glass (as someone has suggested)after ripping out is just a wish. Plenty of still well adhered areas will prevent removal
of large, neat pieces. It ain't pretty!