Great looking job Ron!!Here are pics of when I did my Shelby stripes.
Paint
I used 2 inch dry wall paper tape to line up the center stripe and align everything to center. I then used green painters tape up against the edge of the drywall tape and then removed the drywall tape for the 2 inch center section. I then used the measurements to get the front and back widths. Just take your time and measure measure measure and measure again...
Good Luck and BE safe
Ron