Great idea. I have lots of card stock, and never thought of it. I also saw a similar idea using the left over plastic sprues from plastic figures (ie GW. figures, and now Perry and Victrix used to make buildings as well. I think it was on the Lord of the Rings website called The Last Alliance. The plastic sprues are a bit taller, but when the buildings were finished, they looked fine scale-wise. Also, they might work better for your mold making process...just a thought. I have a whack of these sprues so I might give it a try...due to your inspiration!!