Using metal would be a really bad idea. The loops are spread out on purpose for stray capacitance, for one. The heavy duty cable ties are of commercial quality, they are UV stable. You would be surprised how long they will last. This is a practical solution for a very effective coaxial choke. The only thing I can see that could go wrong in the near future, is if the Cockies got stuck into it. Then again, they can destroy just about anything if they take a liking to it, and they are very intelligent. I'm talking about Cockatoos here in Australia of course.