Bill Kinney <greatketch@...>
PVC is one good choice, another is fiberglass. There is FRP tubing available, and some supplies will sell short pieces cut to length. The advantage of it over PVC is that it can be glassed in easily. Neither epoxy nor polyester resins will reliably stick to PVC, but would bond well with FRP tube. In the unlikely event the chain ever wore through it, it would be easy to patch.
Both would be long lasting. You selection might depend on your method of securing it.