This is a link to an Excel spreadsheet set up for making a truncated cone http://jwilson.coe.uga.edu/EMT725/CarlCone/CarlCone.html
Click on the reference to the person from Australia as it is an Excel formula that only requires inputting 3 measurements. I made several paper patterns first (fitting this exactly is not easy) and then a final one from a foil oven liner. I made one to use with my FeatherFire (I believe already the most efficient alcohol stove on the market) and my initial test indicate a 35% savings in fuel. Later in the fall I'll do a full write up on the patterns, fastening, etc.