I'm getting ready to build some new tanks (and I know all about epoxy and potable water, that's not the issue here ). What I'm wondering about is whether I could use styrofoam as a core material rather than plywood or building out of solid fiberglass. It certainly would be easier to shape and once laminated on both sides be very rigid. It would get away from the issue of core rot which can happen with ply. Thoughts anyone?