To start with use the two center drilled/tapped holes at the back bottom of the windshield. Make a small but permanent small mark between these two holes. This can save your painter hours of grief trying to find center! I actually use about an 1/8th drill bit, marking the center on the body-UNDER- the front seal.
From here you can use 2" tape from front to back. This allows you to see "straight" the stripe from front to back.
The front stripe starts at the cowl roughly 10.5"'s but can be run all the way to 11 to 12"s depending on yours tastes.
Then the stripe will taper down to 8.5"'s to 10.5"'s, again depending on your personnel style.
Paint the entire center of he car, front to back with stripe color. the stripe is then masked off and stripe will be covered in masking paper. The pin stripe is normally placed 1/8th away from the center color. Move to the outside of the stripe, this time lay out another 1/8th" stripe just inside the edge of the outside. Mover outwards and 1/8th " and then mask off the edge of the stripe.
Paint the color of the car, wait about and hour with BC/CC before removing stripes. This is also the formula for the rear stripes, only they will start out anywhere from 91/2"'s to 10/2 inches then these two will taper to the rear and downward.
Believe it or not when done the stripes will appear to be parallel and NO taper is visible to the eyes!
Questions?
P.S. Haven't figured out the "?" mark for the photo's yet. Right click and then open.