First... geeze mon, don't call your life lines "safety fences". Ya won't get no respect, nohow!
But to answer your question, we changed to Dyneema
about three years ago, and like them fine. Had to add some short bits of Davis split PVC shroud
covers where the Dyneema
goes through the tops of the stanchions to stop some chafe, and some longer bits where the genoa sheets
bear on them when the genny is poled out.
Of course, without destructive testing it's hard to know how much their strength has degraded, but 5 years seems to be a folk wisdom life span for the stuff.
We've also used it for the runners and the baby stay with no problems, and are considering it for our backstay when it needs renewing (fractional rig with swept back spreaders so the backstay doesn't do all that much).