"Kevin in San Diego" wrote
Mine have bolts in the cushion board that
go into the boats fiberglass. Then inside the
fiberglass area there is a piece of wood for
a washer and nut holding it on.

Same here, more or less. Mine have a blind nut (like this:
http://www.stafast.com/images/parts_tnuts_4prong.jpg) on the not so blind
side of the cushion's backing board with a machine screw going through it
from inside the padded side. The end of the screw serves as a stud to go
through the fiberglass. There's no backing board behind the fiberglass on
mine, just a fender washer and nut.