Planks to plywood or fiberglass

Have a 52' chris craft its been out of the water for a while,most of the plank on the bottom is gone. I was thinking of replacing the bottom with plywood and then fiberglass or should I use fiberglass core then fiberglass.

 

Take a look at the bottom as a whole. If the planking is as bad as you make it sound, start with the frames and keel before you bother with the planking.

 

This is not to make you feel bad or put you down in any way. But if you have a boat of that size and you are asking complete strangers. Would not the advice of several LOCAL builders come first? They can actually see how bad the rot is. Then ask us for opinions. Yes you can put a couple of layers of plywood staggered on top of one another and the hull would be stronger than steel. But at what total cost? $$ is usually not unlimited.