I bring this up because when I double click on a suit that suit has to determine what character is on the screen on load the appropriate MAT file...? Right?

NO. The thing you are clicking on to apply textures - that is the MAT file. It's a special pose that applies textures. It won't work correctly with the wrong textures or the wrong figure.

UTC creates two files - a texture file, and a MAT pose file. If you are clicking on the old MAT pose, it won't work, except on the nipples (because the material zone names are all different on V2 and V3, only the nipples have the same name).

I think you are using the old V2 MAT pose, when you should be using the new V3 one UTC has created for you.