What is the best support structure for full size polymer clay masks?

I've been using a plaster mold of a commercial plastic mask as my base for sculpting polymer clay masks. I cover the plaster with aluminum foil or sculpture wire so the clay won't stick. I want the mask to be sturdy but not too heavy. Any suggestions?What is the best support structure for full size polymer clay masks?
There is a polymer clay called 'Sculpey UltraLite' which is extremely lightweight (it floats) but durable. It sort of reminds me of stale marshmallows in texture. It does not hold detail very well. However, you could use the UltraLight as a base and add your details with a more detail friendly clay like Premo, Fimo or Kato.What is the best support structure for full size polymer clay masks?
Use the sculpey ultra-lite and gesso it. Sand the gesso to the required smoothness.