Yay! I have the base for the blade complete - I had bought my friend a poster for his birthday, and it came packaged with a huge piece of nice cardboard behind it. I knew I would find a good use for it
I cut two pieces of it - about 3 1/2 feet long, 4 inches wide. I then took my trusty pointy-tooth-death-stick (read: x-acto knife) and scored a line down the middle of each piece, which was then bent in half. Masking tape together. Cut 4 little triangles out of the cardboard, taped those on the end to make the beveled point. Fill with insulating spray-foam, insert dowel rod into foam to set. Tada. Sword base. It's pretty lightweight, only about 3 pounds. Now for the hilt- I'm thinking maybe florist's foam. Model magic is a little hard to work with.