There are....
...nuts that the bolts go through in the cabin. What you'll have to do is peel back some of the hull lining in about the area of the stanchion. Then reach your hand up between the hull and the lip of the ceiling and you'll feel the ends of the bolts. There are some washers to spread the load of the nuts--but they are inadequate. Its a two-person job, one to back the bolts out from the deck, and a person on the inside to hold onto the nuts so they don't turn. There isn't any room to turn the nuts, clearance is somewhat tight and be prepared to drop some hardware into the cabin top, so have spares. When you replace the stanchion, be sure to use some 3M 4200 around the base, and see if you can get some bigger washers or backing plate on the inside.
