With the drywall up and the walls painted, I finally got a design wall up that is stable and usable for larger quilts. I made it out of 1/2" thick foam board insulation and secured it to the wall with screws and washers. It's 8 feet wide by 7 feet long. I had to trim a foot off of one of the pieces of insulation in order to get it to fit. My walls are only 7 feet high.
I'm still reorganizing the quilting space, but it's coming along nicely.