had very good results in fiberglass. I'm thinking about just tapping the fiberglass but putting six or eight of them in close to the bottom where the load will be. That way, when I get somewhere that they aren't needed, I can remove them and just have the 1/4 inch holes to fill. I know that reality strikes and once they are installed they will never be removed. Even though, as Dan says, I won't need them in the caribbean.