If you increase the thickness you are going to get away from the correct quench area which I believe is 35 to 40 thou, thus bringing detonation into play, the copper gaskets are good but from what I have heard water leaks are a pain, there is some stuff called halon in a tube that stays flexible and seals leaks, I might be off on some of this stuff so any one else care to jump as I here the horn for the bus.