deck core ideas for Sea Cat SL3

So the deck of my sea cat is getting spongy in some spots. I plan to just cut the top laminate off the sole, then remove the bad wood core.

These are my choices.

1. replace with marine ply. I was told to cut into 6x6 pieces and then bed down and then glass over.
2. Replace with coosa, I have no idea what panel to use, Nautical 15, 20, Bluwater etc. Most expensive.
3. replace with Nida Core, I'll have to embed aluminum plate where I want to mount things, not a big deal, I have a router and plenty 1/4" alum plate, very inexpensive for a comp core.
4. pour Arjay/Sea cast and then glass on top and imbed some plate. By far this would be the quickest route.

What do you guys think?

Obviously like everyone else I am trying to spend the least money and the least amount of time to get the best outcome.

 

I think I would start cutting out the spongy spots and see how far it goes, the 6 x 6 might be a good first cut but I wouldn't use several 6x6 pieces of replacement material, if say, the deck is rotted in a contiguous area of a few sq feet. I don't like wood, I do like Coosa! Bluewater is dense enough to bed screws in with 5200.

 

I was talking about cutting the whole area out and then laying down 6 inch x 6 inch squares of kiln dried marine treated plywood.

I do like the coosa though despite it being super expensive because I can just lay in bedding compound and then glue the skin I removed right back on top with out having to glass or resin the coosa first.