I would build this helmet in the following order:

1) Cut out the plates.
2) Punch holes in the side/bottom plate for the camail mounting.
3) Finish the plate edges and corners.
4) Dish and shape the top halves.
5) Weld the top halves together.
6) Grind weld flush on the outside and cleanup weld on the inside if needed.
7) Shape the side/bottom plate to fit the helmet top.
8) Weld the side/bottom plate on to the helmet top.
9) Grind weld flush on the outside and cleanup weld on the inside if needed.
10) Polish the helmet. (I use 3M surface conditioning disks)
11) Build bar grill visor and attach it to the helmet.
12) Add leather mounting strip for camail.
13) Add the camail (You're on your own with the camail).

How to print the patterns: From Redhat Linux 5.1 with xv (Should work on any Linux or UNIX with "xv"):     Load the JPEG pattern files into "xv" (example "xv elbow_p1.jpg"). Print the file from "xv" as a grayscale image on a 8.5" X 11" page with the height and width set to 102.50%.  Remember to "Center" the image after setting the height and width set to 102.50%. From MS-Windows 95 :     If you run the program "Imaging" that's under the "Accessories" menu you can load the JPEG pattern files (*.jpg) and save them as MS-Windows Bitmap files (*.bmp). After that load the Bitmap files into "Paint" (which is also under the "Accessories" menu). Then stretch the image 128% both horizontally and vertically. I set all the margins to 0.25 inches, which was as small as the printer driver would allow. It this point I was able to print the pattern so that the squares were 1 inch by 1 inch as they should be.