Choosing a deck core

Hi guys.
I am taking a project boat. It is 1979 49' Marine Trader Pilothouse.
Boat need completely new decks. What thickness of Coosa 26 should I use?
1/2" or 3/4" ? If anybody have experienced with it? Is it a good idea to use this material?

 

For adhession between core and glass Balsa wins hands down . Have you ever tried to rip glass of a balsa core ?? On the other hand foam has this thing of beng able to PEEL off the glass and thats scary !!
Peel is the test foam falls down on badly . low density foams almost come apart if you simply drop the panel on the floor . Even high (h80) density peels real easy as well so from the peel side of the coin look again folks . Always used H80 foam on decks where theres high traffic and h200 under pads for bolt throughs like winchs etc etc . Make the pads big to distribute load . and add layers in steps and feather them to well .

 

Do you know for sure that it is a cored deck? the reason i ask is that a friend has a Marine Trader 36 and everything above the fiberglass hull is glass over plywood. I have no idea if that is typical.
Steve.