Would've never thought about granite. Good idea.Id probably go with granite/marble instead of concrete. Much denser and easy to cut up if you can get ahold of a diamond axis table (most granite shops have them). Also, they make liquid nails for granite now which would be a supurb joining material. Also granite/granite has perfect laminar air flow across it. Thats how I was able to do a 155.7 in a MECA street class with one 18.