A few years ago we built a vertical forge for welding Damascus billets. It worked great and the borax ran out the bottom and didn't eat the wool blanket insulation. The problem was you could only forge about 12 inches and then you would have to do it in stages by sticking the billet through the forge. That meant only working about half of the billet at a time in the press. I am planning on building a rolling mill and have to have the billet hot from one end to the other. So I made a small modification to the forge. I cut a hole in the back of it and added a 6 in diameter pipe and stuck another burner on it. So I still have the high heat of the vertical forge and when I want to stretch out long pieces just fire up the other burner and now it will handle up to about 24 inches. I have a considerably smaller orifice in the second burner which should save on propane cost.