Custom textures for RUP clothing?

I'd like to add some custom (not replace) textures to some of the clothing that comes with EUP. 

Currently, I'm trying to create a custom texture file for the coat located in importexport under the name jbib_001_u.ydd. From what I understand, the textures for this coat are under jbib_diff_001_#_uni, # representing a letter, and the letters for go from A to M.

The texture I am using is meant to replace one of these textures, however all of the .ytd files are already taken up by uniforms I use in-game, so I can't replace any. Now, I assumed that creating a new .ytd file with N as is designating letter ( so it would be: jbib_diff_001_n_uni), and then importing the texture into that would work, but that doesn't seem to be the case.

I was wondering if anyone know if this is something that can be done, and if so how?