Really nice theme - definitely building something for it!
Maybe I'm even going to try to fit a fullspeed map in there, too
I have one question though: You stated, that terraforming can be done outside of the 15^3 box - does that include the "blocks" in Valley's category 6/3, especially 6/3/7, which should be considered a part of the terraforming system (it just alters the looks of the cliff terraforming blocks)?