My wife runs an Internet bookstore out of our house. We've been using bookshelves up to now, but we think we will get more efficient storage by packing them in boxes. We have some already boxed up, and invariably when we get an order, the box with the book is at the bottom of the stack. We've also noticed that we can't stack more than three boxes before the weight crushes the bottom box. I've been considering building racks to store the boxes on and wanted to know what the folks around here thought would be the most economical material to use. What do y'all think about using PVC pipes and fittings, and what diameter pipe would you reccommend using?