+1 vote for chain, and steel rods
The collapsable type with chain are best for durability. Proceed with all due caution. Even if you are expert, I assure you, if you mess up, they can take you out. Not kidding here!
I have been a licensed instructor of 2 Military styles of TKD for about 25ish years. ANYONE is capable of mishaps. Furthermore, in most states, these are NOT legal for defensive purposes. When transporting, they must be secured out of reach.
Personally, I will not use them.
Best of luck and be safe.
Doc2005