i dont know the layout on the Mustang, but on brief look, you may want to put two decals on the nose: one with the lines and details, and one with the colors (looking at the yellow and teh OD green)
then, your details can be one tga thats huge, and the color set can be smaller underneath the detail tga. place the details tga in a common folder, and you only need it in there once.
develop them same sizes , then just scale the final product down on the nose color one. place the detail one last in the decal ini, so it shows on top of the others.
but thats damn sharp for a decal all the same