I test fit a paper template on a car yesterday. They fit perfect.
One thing we did differently is that we made them in two pieces only. A front piece and a door piece. It installs in one piece on the front bumper cover and fender. This way, there is not a body color line running up the middle of the main stripe section. Once it is installed, it can be formed into the joint between the bumper and fender, then a relief cut can be made so the decal does not tear. You might see a very faint line at a certain angle, but it is nowhere near as noticeable as the factory stripes.
We do all of our Challenger stripe this way and have had great results and a better final outcome.
We adjusted the lower front of the stripe to be parallel with the marker light and refit it since these pics were taken.