Homebru, I'll give that a try once the snow melts.
Two Bees, thanks neighbor.
contactme_11, My plan was to buy inner covers. The amount of effort to build them didn't seem justified given their low cost. I also don't have any immediate need for the rest of a piece of plywood, or space to store it. So far, I spent about $60 to build 2 outer covers, 2 bottoms, 10 medium boxes and a gallon of oops rack paint. I'm still well under budget.