Dynex Dux is not immune to UV. Colligo Marine say that it will easily last 5 years and they say this compares to a recommended interval of 8 years for steel. I can't believe very many, if any, cruisers change out their standing rigging
every 8 years. Maybe circumnavigators. I think the performance gain on a 1973 Cat 27 is going to be overshadowed by the likely shorter life, and thus much higher total cost.