Wow, thanks! I had looked into the foam walls before, but I decided on cardboard because I've been hoarding it in my garage, for a few years, for projects (much to my wife's dismay).
But seeing how cheap the foam is, I think it's time to get started. I've got all of my measurements down for the Clock Tower, and the cosmetics can be easily transferred.
Thanks again G.I.! I'll keep you updated!