Enclosing the underbelly: a few design questions

Some more great tips -- thanks! JBarca, by jam nuts, do you mean nylon core nuts??

And deadticket, I like the double tape idea. The corrugated panels (coroplast) can be found in big hardware stores or online. They come in various thicknesses.

So here is another question -- if I seal the bottom with coroplast, what happens if there is condensation from the outside of the water tank? Won't it puddle up on top of the plastic??