A couple of quick points.
First, a simple way to tell if it is a SeaCraft or not is to look at the hull. If it does not possess that patented variable dead rise hull than it is not a SeaCraft.
We have seen many fake Seacrafts out there.
Click here for a copy of the hull patent
web page
Second, having owned two Potter built SeaCraft's I would not describe them as tanks in terms of hitting them at the side of the hull and saying "wow, that's solid fiberglass". In fact IMO there are many other boats out there that feel more like tanks.
Here is the rub. The SeaCraft's are bult like tanks where they need to be built like tanks. My old 1978 23' SF SeaCraft had an original floor with some soft spots. However, when you put that baby in the ocean and took her for a spin she was a rock, with a smooth as silk ride.