The artwork for the banners with the various XP has shown some weirdness, and I did a bit of question asking and now some tinkering.
The banner box, if set to 7.5 inches across and 2.7 inches tall will fit as designed.
The transparent background to the banners is grey, not white.
Screen shot of the creation process.
I do not recommend making a hard border, as above. But, it is nice to have a clue as to where to put the art so it displays well.
Now, back to the grindstone!