I've made one prototype 8-yd knife pleat. As expected, it was a learning experience. I made it out of a reasonably heavy fabric from a large chain that regularly advertises in the comic pages of 2 of Toronto's papers. Recently I picked up some wool/viscose tartan from them. It was a bolt end and (amazingly) the selvedges were in good shape. I'm planning on doing a 4-5 yard box pleat with it. Just trying to work out how to taper it.