I have worked with various recipes of Hypertufa for a number of small projects and they all turned out well. Now, I am looking at a muuuuuuucchhh bigger project this comming Spring. I am planning on making several standing stones. They will have cores made of foam blocks 'glued' together with Great Stuff. The blocks originally measured 12"x12"x18" and the 'stones' cores now range from 3 to 7 foot tall. I was thinking about Hypertufa to cover the cores because I really like how natural it looks when fully cured. The spring and fall tend to be wet, the summer hot and dry and the winters can be brutally cold. I don't want to have the shells crack and deteriorate rapidly. Are there any recommendations on the recipe to use for this... or a recommedation to use something else?