Oddly, I found very long, narrow decals to be fairly easy to fit. The trick was to slide a small bit off the end of the paper, hold that in place and then pull the paper out from under the decal.
About ten years ago, I built
this for my brother, one of whose main hobbies is
this site and its contents:
View attachment 193227View attachment 193226
The entire
The Book of Souls World Tour on each side is one long, thin decal, and less visible is that there are also decals over the whole rows of windows, both to "glaze" them and to have a neat, printed black outline for them. All except one of those went on without a hitch — the real trouble was the large decals on the tail fin, which needed a lot of Micro Sol to conform to the surface.