Re: how to install a deck?
I have a chrysler, 20' center console, they don't use 2x4's under the deck.
More likely it had 3/4" plywood set vertical, not on the keel. Keels are usually left open for drainage.
The problem is the 2x4's are not glassed, they're already wet with standing water, they probably need to come out.
You likely have 3 feet of snow on it by now so time to do a bit of research on the original construction.
Its only a 14' hull so I wouldn't bother copying designs from bigger hulls, it probably had two stringers and a couple of cross braces or ribs.
Leave the foam out of the space between the stringers for drainage.
Get it all cleaned out and look for the tell tale signs for the original construction on the hull glass.
Where in rhode Island are you ?