peate
Hi !
You can have as many material layers as you like 🙂
You don't set envelope on any of them to 0.
You can think of zMaterials as layers in photoshop; i.e. you can make a zMaterial 'transparent' (ineffective) by painting it's weightmap to 0.
So with special regard to the fat: You can just set the properties of your base zMaterial to be whatever materiality you want to see in the fat.
Then add another zMaterial, and make sure the vertices on the inside only are painted to white (everything else black). So then on that new zMaterial, you can add pressure/surface tension to make it suck in.
Here's our talk at FMX this year, I talk about skin at around the 20 minute mark.