A template was made from butcher paper but working alone with a span of over 8' made it a little tricky. Using a stapler I was able to tack the rough template making slight adjustments using a utility knife. With the staples carefully removed the template was then transferred to a thin (1/16") piece of particle board. A jigsaw did a great job with a fine toothed blade followed by hole drilled at center line to accommodate a small finish nail allowing the 2nd template to be fitted and verified. Two more small holes (top) were then drilled to support the template and keeping it flat on the header.
Once it looked good the template was pulled leaving the three small (headless) finishing nails.
I found a remnant piece of 14 gauge plate that was long enough since I needed 97" X 18". The pattern didn't allow for mr to break a 90º return so it required welding.
I use this ArcZone tungsten sharpener. It provides a very nice point with a steep angle.
The material was set up to provide a corner joint. I wanted to blend the weld for a clean outside corner.
You can see the 1/16" filler was slightly bigger than the joint but did a good job filling. Back step welding technique was used to keep unwanted distortion.
This shows the amount of back welding and skipping around based on the heat zones. Usually about 3" runs worked for this application.
After blending with a 2" 60 grit rol-loc on a die grinder followed up with 150 grit on a DA the corner looks to be one piece.
The iron clad was installed and sealed with siliconized paintable caulk. Small truss head screws were used temporarily installed to allow the caulk to cure.
Next the final step...