oh! and if you want a heavier material than the casa satin try this:
Dull Bridal Satin
It's easy to work with, a medium heavy weight material, and its not as shiny as the traditional satins out there. Also the seller, Syfabrics, is great! The material I've gotten from them has always been wonderful and reasonably priced. Not to mention I get my package within 2 days of ordering (I live in SoCal)
Have fun this is a charming costume!