I liked the design of this box, but I saw some room for improvement. I rewrote the code from scratch to add the following features:

• Add holes right up to the corners--this saves an additional 15 to 20% of plastic and I think it looks a bit nicer.
• Parameters for things like hole size and spacing.
• Holes are automatically generated and should fill any size box.
• Added angles under horizontal surfaces to allow printing without supports.
  The customizer has a little trouble rendering but it should generate a good model.