I personally just open the V3 MAT file in a text editor, make three copies of SkinTorso (only because that's usually the first one in the list) and rename them to SkinThigh, SkinShin, and SkinKnee. Then I save the MAT file again. The new MAT will still work for victoria 3 but it will also work for all the other unimesh figures too. You don't need to make a seperate MAT for all those characters, in fact in my MAT pose directory I just have them all grouped under one folder called Unimesh.