I think that it is safe to say that with any stencil stripe kit, you should expect to spend some quality time with thin blue painter's tape in order to get all the edges and gaps just as they should be.
I know that was true for the DX1 stencil stripe template used by the restoration shop on my '69 RS back in 2014. The restoration shop sourced the stencil kit so I'm not sure where they got it from, but they spent a good four hours getting it correct on the car, i.e. to get all of the edges to line up properly across panels and the gap above and below the 327 fender engine badge to be spaced correctly.
.....and yes, I did put the stripe under the clear coat - just made better sense for my car.
Richard