Applying Decals Over Irregular Surfaces

Painting it is a good option. In fact the more that can be painted, the more control you have over weathering and a scale look.

Yeah, it's a very weird surface.  If you look at the trail edge of the stripe at the top of the vertical stabilzer in the picture I have linked, you'll see the curvature I'm talking about.  I'm probably going to have to just paint it.

https://upload.wikimedia.org/wikipedia/commons/e/e6/F-15%2C_71st_Fighter_Squadron%2C_in_flight.JPG

I use two methods.  Often slitting the decal at the edge helps, especially for a single curvature area.  Or, if paint available matches the color of the decal, I will just trim the decal off at the end, and paint it.  Sheens will likely not match, but a clearcoat evens out the edge.  There are occasions where a kit decal just plain will not work, as on an ogive nose (double curvature area with sharp curves). In this case painting is a better solution than carving up the decal and trying to get it to set.