Dyneema for running back stay ?

[wklein]

Hmm, that's not exactly a quantified measure is it. I'll bet that covered dyneema has a lot better UV resistance than uncovered, and that both have poor UV resistance compared to wire. Personally I wouldn't use anything but wire for standing rigging which is going to be outside all the time. YMMV!

Dyneema is an excellent material for runners, it is as uv stable as polyester on paper and in practice. it wont attack your mast when stowed either. i would cover it at the spreaders with chaffe cover or leather though.