To the extent of my knowledge, FPSCR models only use 1 texture file.
Unless someone else has a method for using multiple textures in fpscr,
I'd suggest reworking a single uv map and embed the textures where required.
Here is an awesome tutorial from start to finish.
I believe video 4 will steer you in the right direction for textures.
http://fpscrforum.thegamecreators.com/?m=forum_view&t=208184&b=8