Sometimes or, as my wife will tell you, most of the time, once I get going on a project I am driven to get it done. In this case I got ahead of myself - the screw holes were not sanded flat, meaning the film would not iron down properly. And the marks I made to guide the stripes would not come completely off.
So, I've taken a step back.
Sanded the holes flush...
Removed as much of the marker as I could...
Scuffed the whole thing for some more coats of paint.
When the painting is (re-) done I will give it a longer curing time and find another way of marking the path for the stripes.