The "benchs" in my jons boat are more or less fully enclosed. Given that there is no access to the underside of the bench top to install washers and nut, what is the best way to mount pedistal seat bases. I have my doubts that sheet metal screws would hold.
Cut an access hole in the side of the bench seat. You can install a hatch cover to cover the hole. You’ll also gain some storage area if the bench isn’t loaded with foam.