Yeah, California seems to be really paranoid, rightly or wrongly, about a lot of stuff. I'm surprised that you can find the white styrofoam, as I think that it's not that much different in its composition. I just read in today's newspaper that Ar-nold is in Toronto today - maybe I'll pop over there and tell him to pick up some blue stuff for you while he's in town; after all, I believe he's here on a trade mission. :mrgreen: :mrgreen:
I don't use foam, but would suggest that you try to see if you can find someone who can bring some in for you. Don't use the white foam: it's messy and has virtually no strength. Plywood makes a good solid base and plaster over screen probably is less messy than the white foam, and a whole lot more fun to use.
I'm really surprised that this stuff is banned outright: in Canada, many new homes are sheathed in it, as its insulation value is higher than fibreglass. I used it on the inside of my house, where the rafters form part of the ceilings, and it's also an approved vapour barrier in Canada.
Wayne