Thanks, Pottz, Barb, and Bently!
Barb, you can't possibly be serious. Mini Wheat biscuits are stable in all three dimensions. A Cheerio is stable in just one. Using a Cheerio box spacer at the wrong orientation would have caused the two rack halves to roll away from one another, making the hinges all wonky. :-)
Bently, I don't do anything quickly (except writing things). It took me almost a month to finish this thing (not including the initial design work).