At 06:11 PM 8/19/2010, neil n wrote:
>Dow (Canada) claims their product has excellent moisture resistance.
>
>http://building.dow.com/na/en/products/insulation/styrospan.htm

Any of the cast Styrofoam products will be waterproof.  Any sintered
pre-expanded-bead product will not.  If you want one that's
definitely extremely waterproof, get a chunk of the stuff they make
for pier floats and similar.  Try to find some place that has cutoffs
or scraps, as a billet of the stuff is probably $100 or better.

To bend a board to conform to wall curvature, kerf it on the inside,
i.e. make saw cuts perpendicular to the bend direction that don't
quite reach the other side, but have sufficient width that the kerf
will just close when the panel is bent to the desired degree.

Suggest a few little dots or lines of Liquid Nails (checking
compatibility) or similar -- foam will tear off them when you need to
remove, and you can then scrape off the adhesive.  Or likewise glue
on some Velcro strips.

Yours,
David