I sell the hard fabric storage boards on this site:
http://www.quiltingboard.com/t-99292-1.htm
But, I also use lateral file cabinets as additional storage like you're doing. Isn't it great. To protect your fabric, I recommend you Google "comic boards" and purchase the acid free type. They're very reasonably priced and work great to cover your hanging folders. These comic boards are really too flimsy to work standing up and wrapping fabric around, but they work great protect fabric the way you will be using them. You'll have to tape two together and hang them over the metal bars. Just put the tape side towards the metal bar and you're good to go. Love the way you fashioned the drawer fronts too.
You and your sister are very creative - can't wait to see what you come up with next. Nicely done!
Hugs,
Gayle