It's always nice to see a fellow prop builder that uses cardstock and to excellent effect. I know this thread is a little older but If you read this I would love to trade some ideas. I know I have discovered alot of tricks and tools to make cardboard viable and would love to see if you have come up with any ideas I have not thought of.
I would definately love to find out what type of cardstock you are using as I have had trouble finding inexpensive options for large sheets. Right now I use only computer paper.