I think the stickers will be easier to paint than the gaps between the units.
I would want to have that area black to mimic the negative space.
I've fixed that issue using a Staedtler Black Pigment Liner with a 0.05" tip. Picked it up at our local craft store. The tip fits perfectly between the lifts.
And, another issue I have with those loads is the incorrect placement of the strapping. Those are only used to secure one lift to one above or below it, not to itself. The ones on the Prairie Shadows loads are all, or mostly, incorrect.
Doug