Well these old eyes are having trouble seeing it but I'll throw out a thought.
The CCPs had foam flotation between the stringers. Since this is the same hull, I'm thinking the XFs might have had it too (my 91 WAC does not). Over the years the foam has been known to absorb water and if this is the case, it could be causing the "bulge" you see in the deck. Again, I don't know if that's the case with this hull.
Water enters the foam via poorly sealed deck penetrations. Still, that doesn't appear to be the case in the pic you have posted.
Are the helm pedestal seats mounted directly to the deck?