Laying teak decking (to look like a real deck) over a fiberglass deck . . . Decking was 1/4 or maybe 3/8 laid in glue (can't tell you what) and held down with battens that were screwed into the gaps between the "planks." Once the glue had set, the screws were backed out, holes filled, and the black caulk laid in. No fasteners/bungs used except in the covering boards and inboard. Not sure how you get around that except perhaps with weights?