When we built out my 16ft big jon several years ago, we used 3/4 inch plywood + resin + fiberglass matting.
Precut everything, then glassed it. wrapped them in carpet and screwed it all together. The matting really gives the resin it's strength. If you don't want to go that far at least do something other than just wrapping the wood with carpet to keep water from rotting it out. Even if its a simple waterproofing spray or roll-on.
But since it's a back deck and not a mid-deck the chances of it needing to be sturdy enough to support weight are higher.
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