Zip ties are a PIA to remove if they're applied properly. Nail scissors do work but it takes time. I really like the idea of double zip ties.

A thief is looking for quick and easy entry into a bag. It's just like a house. You can't make your house theft-proof but you can provide deterrents.

There's no way to make your checked bag completely safe. However, you can make the thief look for that "unlocked door" instead of your "deadbolted door with a security light."