There is a CS 36 "Traditional" which was produced prior to the Merlin and is probably a better sea boat. It does not have a cored hull
The Corbin hulls were strongly built but most of the hulls were sold as kits hence the quality varies widely from boat to boat. I think the Corbin hulls are cored as well.
From Canadian Yachting Magazine: "...Corbin elected to use encapsulated ballast in his hulls – a common boat-building method, but one that can make a hull
vulnerable in a serious grounding as there is no external ballast to absorb the shock of a big bump. Corbin boasts, however, that he has added eight layers of fiberglass
between the ballast and the hull so that his boat will not sink if the fiberglass keel
is damaged. Overall, the laminate schedule of the Corbin (the recipe for how much glass to use in the hull) is impressive, calling for 11 layers of fiberglass mat or roving, in addition to a 16 mm Airex core
Gozzards and Bayfields are both great choices, the Bayfield could be considered the "entry level" version of the Gozzard. Both are Ted Gozzard products. The smaller Bayfields have a reputation for being slow and a bit stiff, but they handle weather
well. The Gozzards are very well-built boats, not the fastest things afloat certainly but they are nice and seaworthy
The Bayfield and the Gozzard should easily accomodate swim platforms. The Sabre
and the CS Traditional MIGHT be able to accomodate one but the Corbin has a canoe stern.
The boats you have selected cover a broad price
range. This might be something to consider too...