I was also trying to decide if its worth having it laid out so you can fold the note to cover the private key.
If you get a nice design, please post it. In the mean time, I got my hands on a business card holder that opens on a side, so I can put the bills with the qr code first. When I need one, I only extract haft the bills, enough to see the numbers on them, but not also the QR code. If someone can manage to steal the key in this way, they deserve the coins