Between the IR and the IS is a very light pencil tick mark. This is the measured center of the IRIS decal.
The body tube also has a very light pencil tick at the center of the upper white rectangle.
This makes it easier to center the decal by matching up the two tick marks. Sometimes a drying decal doesn't give you much time to move it around or check the center with a ruler.
After the rear black decal was set in place, a line of the white background showed around the edges.
A little touch up with a fine point Sharpie covered up the white line.
You can clearly see the difference between the gloss black painted surface and the matte finish of the decal. I'll have to give the model a clear coat to even this out.