I did a few tests:

probably a bug: invisible models are visible (I use them for collision in some cases).

I had similar problems with actions: I set terrain material from its action depending on its skin quantity, to single skin or a multiskin (effect=terraintex.fx;) material, but it does not work (probably because it has no while loop), despite the fact the assigned material name appears well in $$m and wmb too... I will make more trials to describe it better (or maybe a simple stupid while loop helps).