Bob - you raise a good question. I assumed that the J's with the wooden floors were solid wood and not lam'd on to the fiberglass pan.
Screwed and plugged and then maybe a bit of adhesive? .... BUT prior owners have a tendancy to sand off old finish and wood to make like new ... wearing down through the plugs to the screws heads ... ugly. for those thinking of refinishing ... varnish remover!
But I would explore:
Plastic teak and holly I'm thinking a lot of new boats are going sort of this way to save weight. Matt would be my choice.
BUT what do the non wood floor models do for the bilge cover?