help with bodyslide nifskope mesh?

[tareo1]

So basically I made my own armour set by combining parts of various other armour sets for my own use. However, the different parts have an inertia that seems to be connected only to the individual parts (such as a belt that moves around independently of another belt underneath it). How do you like combine meshes (in photoshop it's the flatten function) to make them move around as a single object? Basically combine both belts and the base underarmour as one piece?