i would have just added to the top that was already secured to it if it was sound and not rotten. get you some metal tapping screws and re fit the og top. then double that for the vice. your vice will most likley see downward pressure. you could always use a good wood glue and screws to laminate the two plys.. but not nessary. if it was a floor you walked on every day sure. keeps the sqweek at bay!