The factory screwed the seaboard stops directly to the balsa core bottom. Water penetrated and there was some rot from 1/2 to 1+ inches in diameter around the screws. Some were OK. I removed the rot, filled the voids with thickened epoxy and set the new screws into the epoxy. I also drilled out the OK screws too. Basically its the procedure for attaching anything to wood core fiberglass.
The floor stays clean enough. Nothing penetrates it. The boards butt against one another and sand and grit can collect in the seams a bit, but it brushes out easily. Under the dinette, where we don't walk, it is pristine. I originally finished it with Deks Ole part 1, a Norwegan product that seals and protects wood but does not make a glossy finish. You need to recoat it yearly. I've used Deks Ole on wood floors in antique boats with success.
I had the floor out and pressure washed it which gave it a bit of unwanted texture. I have since given it a coat of thinned spar varnish; a bit more durable finish. When I get home I will pull it out, it removes easily, and ponder the next step in it's evolution. It sits on little joists and is flat. I really like that. I did not like walking on the sloping fiberglass floor. When I got the boat it had carpet cut to fit and laying on the floor, and it was constantly loose under my feet. If I had glued it down it would have make it much harder to clean. Carpet can hold a lot of crud. I like my wood floor.
Carpy